Embedded Systems with Microcontrollers

Microcontrollers in Embedded Systems

 Online Since 1996        This Page Last Revised 24 Jan 2000  

Microcontroller FAQ

Archive-name: microcontroller-faq/8051
Posting-Frequency: weekly
Official home location for this FAQ: http://Microcontroller.com/embedded/references/faqs/microcontroller-faq.htm
Present Author: Bill Giovino/FAQs Manager faqs@microcontroller.com

This article is a primer and general FAQ about embedded processors and microcontrollers.
Included is a collection of information sources.

The following topics are addressed:

       0)  Rantings and ravings (to make the FAQ zero-based)

       1)  ABOUT THIS FAQ
     1.1)  Who put this FAQ together?
     1.2)  How can I contribute to this FAQ?
     1.3)  What newsgroups will this FAQ be posted to?
     1.4)  May I distribute this FAQ or post it somewhere else?

     2.1)  What is a Microcontroller?
     2.2)  Applications
     2.3)  Flavors

     3.1)  Shipments
     3.2)  Industrial applications
     3.3)  Deciding whose microcontroller to use
     3.4)  The players

     4.1)  Fabrication techniques
     4.2)  Architectural features
     4.3)  Advanced Memory options
     4.4)  Power Management and Low Voltage
     4.5)  I/O
     4.6)  Interrupts
     4.7)  Special microcontroller features


     6.1)  Evaluation Kits/Boards
     6.2)  Easy chips to use
     6.3)  Software (cheap and easy)

     7.1)  Machine/Assembly language
     7.2)  Interpreters
     7.3)  Compilers
     7.4)  Fuzzy Logic and Neural Networks

     8.1)  Simulators
     8.2)  Resident Debuggers
     8.3)  Emulators
     8.4)  Good Stereo System

     9.1)  Books
     9.2)  Data and Reference Books
     9.3)  Periodicals
     9.4)  USENET newsgroups
     9.5)  Internet sources of information on specific microcontrollers

    10.1)  FTP sites
    10.2)  WEB pages
    10.2)  BBSs
    10.3)  Mailing lists


0)  Rantings and ravings

    Disclaimer:  Just so it is understood, the "rantings and ravings" are
    my rantings and ravings.  My readers are refined and sophisticated
    and would never rant or rave.  I, on the other hand, sit in front of
    the TV in torn underwear and drink beer out of the bottle.

    =====> OK, I know this FAQ is long. Very long. Well... it's
    ridiculously long. If you are inconvenienced or strenuously object to
    the posting of this FAQ, please DON'T FLAME me or send me nasty mail.
    Just think what I have to go through. This FAQ takes a lot of my
    time, of which I have very little to spare. I'm open for suggestions.
    I've considered the following:
        - splitting it up into smaller parts
        - eliminating certain sections which may no longer be relevant -
          the web and search engines certainly seem to make a lot of this
          FAQ obsolete (or am I mistaken on this?)
        - not posting it to the newsgroups and just turning this
          whole mess into a [large] web page (the problem with this
          is that I don't have a web site)
        - forgetting about it all together and reminding my kids that I'm
          their father (if you all tell me to go packing, I'll gladly
          fold up shop and devote more time to family, friends, and
          personal hygiene)
    I would be happy to hear ideas on how this FAQ could be improved for
    the reader. If it makes MY job easier, then that's even better.

    OK, with that out of the way, let's get on with it...

    Techno-Wimp, has announced the next generation of their wildly
    successful MIL (Mother-In-Law) transducer.  Dubbed the MIL-II, it now
    includes Techno-Wimp's proprietary new breakthrough technology, MMX
    (Mad Mother-in-law Extensions).  Utilizing patented heuristic
    algorithms, the MIL-II achieves a remarkable performance rating of 15
    million MIPS (Mother-In-law Periphery Scans) per second.  The
    previous WOMF ("Whoa, outta my face!") technology has been updated
    and improved, and together with MMX permits the MIL-II to
    concurrently detect multiple stimuli. This provides the designer with
    the necessary safety margin when using the MIL-II in mission critical

    The MIL-II is implemented in Techno-Wimp's patented new fabrication
    technique, 0.25 micron JMOS (Jello Mold On Silicon). The MIL-II also
    features a new packaging technique called PSC/CEC (Plastic Slip
    Covers with Card Edge Connector). PSC/CEC was designed to allow easy
    upgrading to future products in the MIL transducer line.

    I hate it when I'm stupid, and well, I really did it this time. I
    omitted an important source of information - EDN magazine. Always
    full of timely features, important design articles, and the popular
    Design Ideas column. In addition, the 24th edition of the EDN
    microprocessor directory is due out this fall. This directory is an
    invaluable aid for designers. The EDN web site also has a lot of
    important information and software, and is improving all the time.
    Worth taking a look at:  http://www.ednmag.com/

    UMPS (Universal Microcontroller Program Simulator) is a new package
    from Virtual Micro Design in France. It simulates the following
    microcontrollers: 8051, 68HC705, PIC, ST62xx, and the 68HC11. The
    main feature of UMPS is the ability to build a virtual
    microcontroller board on screen by connecting various virtual
    resources (switches, LEDs, displays, A/D, D/A, I2C devices, logic
    functions, etc.) together with the desired processor. Then when
    debugging your software, you can see "real results" without having to
    worry about actually building the hardware.

    Processors that are not supported can be added by the user using
    Virtual Micro Design's toolkit. Additional virtual resources can be
    added by writing your own DLL to support the desired device.

    UMPS includes an integrated assembler/disassembler and debugger,
    extensive documentation on the supported processors.

    This is a very slick package. The English needs a lot of work, but
    the software itself is first class, easy to use, and incredibly
    powerful. For more information:
         Virtual Micro Design
         Technopole Izarbel
         64210 BIDART
         ++33-559-438-458   Fax: ++33-559-438-401
         Email: p.techer@idls.izarbel.tm.fr

    If you'd like to start learning about microcontrollers, but the
    thought of finding all the parts and then building one scares you,
    take a look at the line of boards available from American Educational
    Systems. They have three boards: AES-51 (8051), AES-11 (68hc11), and
    AES-88 (8088). All three boards are built along the same lines and
    include RAM, ROM, LCD display, keypad, A/D, serial ports, digital I/O
    ports, and logic probe. Also included is a full bookshelf of
    documentation. These boards are ridiculously easy to use and program
    - you can get started experimenting right away.

    This is a perfect system for students and hobbyists. Even
    professionals will find this system useful as a prototyping tool and
    test bed. Highly recommended.

    For more information, contact:
          American Educational Systems
          970 West 17th St.
          Santa Ana, CA  92706  USA
          (800)730-3232 or (714)550-8094   Fax: (714)550-9941

    Check out Peter H. Anderson's web site. Lots of good microcontroller
    interfacing ideas and plans, PIC projects, and miscellaneous

    Barry Kauler, of GOOFEE fame, has done it again. He's written another
    RTOS, called CREEM. (He must stay up weeks thinking up names for this
    stuff. The names probably come to him in nightmares.) As hes says
    about this new system, "It's very unusual and very easy to use. It is
    probably the easiest way yet that anyone has come up with to do
    concurrent (multitasking) programming on a microcontroller." The
    first version is for the 8051 and is only 560 bytes and will run in a
    chip with only the internal RAM.

    Read the intro page and download CREEM (with source code) from the
    GOOFEE web site:

    Point your browser at http://www.debco.com/ and take a look at what
    the gang at Debco has to offer. Lots of parts, kits, and assorted
    computer hardware. The best part is the series of Electronic
    Experimentors Journals that they've made available on-line. Chock
    full of project plans, ham radio topics (antennas and QRP), and
    computer questions and answers, these on-line journals are (IMHO) one
    of the highlights of the web. The gang at Debco should be commended.
    Recommended reading.

    Michael Dolinsky, Ph.D. and his team at Scaryna's Gomel State
    University in Belarus, have been doing research in embedded systems
    development tools. This research proposes methods, tools, and
    application results for integrated design of embedded
    hardware-software systems. Methods include tuning on selected
    hardware and designing hardware in parallel with the software.

    For information on this research, entitled, "High-Level Design Of
    Embedded Hardware-Software Systems",  check out the following web
    Their Inter Demo Version is available by anonymous ftp at:
         borneo.gmd.de (
         cd pub/SYDIS/inter

    Microtec announces a new quarterly newsletter, "Newbits" as a forum
    for their customers to share ideas:

    Take a peak at Magnus Danielson's collection of CPU stuff at:

    Good news... After reading about the 1 bit powerhouse (MC14500) in
    this FAQ, Christian Brunschen checked out Motorola's web site. "lo
    and behold I found,at
    , a
    document called 'Commercial Components' with a remark 'Effective
    date: July 5, 1997'. On page 5 (of 10) there is a line stating
          MC14500BCP      CMOS 1-BIT ICU
    plus some codes, stating that this was a Proprietary device, part of
    something called the 'Phoenix Program', and that the $200 order
    minimum was waived -- but nothing about it being out of production.
    Rather, the'effective date' of july 5, 1997, would indicate that the
    chip is actually being produced as I am writing this. Also, the
    'Phoenix Program' sounds like it could be some sort of 'let's revive
    some chips which we took out or production, just because' (Phoenix
    was the bird who died by fire every evening, and reborn from the
    ashes in the morning, if I recall correctly), so this could very well
    mean that production of this chip has been reinstated. Alas, I have
    not been able to find out any more info on Motorola's site as to what
    this 'Phoenix Program'_actually_ is."

    And you won't believe this, but Scott Finneran ALSO wrote about the
    14500. Looks like we'll have to start a USENET newsgroup on this

    Scott writes...

    "The Motorolla 14500 is alive and well down-under. I recently (about
    a year ago) performed some contract work for an Australian power
    station called Loy-Yang 'B'. They have a system manufactured in the
    early 1980's consisting of amongst other things hundreds of modules
    containing 14500 processors. These little beasts run at a whopping
    speed of 1KHz (liquid nitrogen coolant system was not necessary!!)
    and are used to control the start-up sequencing logic for firing up
    the power station boilers and turbines. The processor module in this
    system contained three 4-bit EPROMs in parallel (the early PICs were
    12-bit I believe... spooky!). The first EPROM contained the op-code
    for the processor while the other two contained an 8-bit operand.
    Note: the operand was never fed into the processor (remember it is a
    single bit device) but directly out onto a parallel bus to select
    from a variety of digital inputs and outputs whose value was fed into
    the 1-bit data-bus of the processor.

    "My work involved reverse engineering their compiler to run on an
    MS-DOS platform. The "language" was basically boolean logic equations
    with little features such as software based flip-flops and hardware
    based timers. The compiler produced 14500 assembly language which was
    fed into the assembler that I also wrote as part of the package. With
    only sixteen instructions and 1 addressing mode, the assembler wasn't
    exactly a lot of work to produce.

    The system (and my compiler) are still in use today. The only
    problems are apparently the occasional timing capacitor goes dry in
    the 1KHz clock generator circuit (yes it's a 555)."

    Well, let's all scrap our '51 and hc11 projects and move to the
    14500. Looks like we've got a trend here. Who knows, maybe Motorola
    will release a new generation 2-bit version? :-))

    Embedded.com is the on-line union of three embedded information
    sources, Embedded Systems Programming Magazine, Miller Freeman
    Directories, and the Embedded Systems Conferences. There is no charge
    to users of this site, which contains hands-on articles, editorials,
    and code downloads.

    Vasu Srinivasan recommends the book "Using the M68HC11
    Microcontroller: A Guide to Interfacing and Programming" from
    Prentice-Hall. He says this book is useful if you're considering
    using the 68HC11EVB. See section 9.1 in this FAQ more information on
    this book.

    Take care of yourselves,

              Uncle Russ


1.1)  Who put this FAQ together?

    From time to time, general questions about microcontrollers and
    embedded processors (from beginners to experienced designers) pop up
    in the newsgroups.  It seemed that a general primer/FAQ might be

    Much of this document could be considered as a sort of a primer on
    microcontrollers, with some material on embedded processors being
    slowly added.  For those of you with previous experience, sections 9
    and 10 might be of special interest (especially for those of you
    looking for that elusive "free COBOL compiler for the 1802").

1.2)  How can I contribute to this list?

    I please ask that if you have any suggestions or additions, or you
    would like to correct any of the information contained herein, please
    send me a note.
         My Email address is: russ@shani.net
         My Smail address is:
               Russ Hersch
               HaVradim 11
               Ginot Shomron

    Thanks to recent contributors:
          Magnus Danielson
          Marius Gafen (NSI, Israel)
          Michael Dolinsky, Ph.D. (Scaryna's Gomel State University,
          Barry Kauler (the GOOFEE guy)
          Christian Brunschen
          Michael Markowitz (EDN magazine)
          Mark Meyer (American Educational Systems)
          Philippe Techer (Virtual Micro Design)
          Thomas Vegeby
          Ron Fredericks (editor, Software Forum Newsletter)
          Leticia Smith (webmaster, embedded.com)
          Bo Eriksson (Uppsala University, Sweden)
          Henry Spencer
          Mihai-Costin Manolescu
          Vasu Srinivasan
          Scott Finneran
          Tarjei T. Jensen
          John Doe (Techno-Wimp)

    Very special thanks to Robin L. Getz (National Semiconductor) who
    probably could be considered an honorary co-author of this FAQ. :-)

    Also, thanks to those who have posted questions and to those who have
    posted answers.  Thanks to "all my net friends" who send suggestions
    and encouragement, as well as the occasional question.  Special
    thanks to my mother-in-law, who thankfully doesn't know this FAQ
    exists ;-).

1.3)  What newsgroups will this FAQ be posted to?

    This FAQ will be posted to the following newsgroups:

    I will post once a month - on or about the 26th of each month.

1.4)  May I distribute this FAQ or post it somewhere else?

    I am putting no restrictions on the use of this FAQ except - It must
    be distributed in its entirety with the copyright notice, and no
    financial gain may be realized from it.  After all, I have spent, and
    continue to spend, a lot of time on this.

    For this reason I have appended a copyright statement to the end of
    this FAQ.  I feel pretty silly doing this, but I just want to protect
    myself.  The copyright does not limit the use of this list for
    noncommercial purposes.  I hereby give my permission to one and all
    to pass this list around and post it wherever you want - as long as
    it is not for financial gain.

        Thank you.


2.1)  What is a Microcontroller?

    A controller is used to control (makes sense!) some process or aspect
    of the environment.  A typical microcontroller application is the
    monitoring of my house.  As the temperature rises, the controller
    causes the windows to open.  If the temperature goes above a certain
    threshold, the air conditioner is activated.  If the system detects
    my mother-in-law approaching, the doors are locked and the windows
    barred.  In addition, upon detecting that my computer is turned on,
    the stereo turns on at a deafening volume (for more on this, see the
    section on development tools).

    At one time, controllers were built exclusively from logic
    components, and were usually large, heavy boxes (before this, they
    were even bigger, more complex analog monstrosities).  Later on,
    microprocessors were used and the entire controller could fit on a
    small circuit board.  This is still common - you can find many [good]
    controllers powered by one of the many common microprocessors
    (including Zilog Z80, Intel 8088, Motorola 6809, and others).

    As the process of miniaturization continued, all of the components
    needed for a controller were built right onto one chip.  A one chip
    computer, or microcontroller was born.  A microcontroller is a highly
    integrated chip which includes, on one chip, all or most of the parts
    needed for a controller.  The microcontroller could be called a
    "one-chip solution".  It typically includes:
          CPU (central processing unit)
          RAM (Random Access Memory)
          EPROM/PROM/ROM (Erasable Programmable Read Only Memory)
          I/O (input/output) - serial and parallel
          interrupt controller

    By only including the features specific to the task (control), cost
    is relatively low.  A typical microcontroller has bit manipulation
    instructions, easy and direct access to I/O (input/output), and quick
    and efficient interrupt processing.  Microcontrollers are a "one-chip
    solution" which drastically reduces parts count and design costs.

2.2)  What is an embedded controller?

    Hah!  Why not ask an easy question like "Did Adam have a navel?" or
    "Did Eve?"  

    Simply (and naively stated) an embedded controller is a controller
    that is embedded in a greater system.  A rigid definition is
    difficult if not impossible to formulate, since the usual response is
    "most embedded controllers are...".  The problem here is "most".  We
    can't seem to shake that word from the definition.  No matter how
    clever you feel your definition is, some wiseguy will come along and
    find an exception, or two, or 50.

    You COULD say that an embedded controller is a controller (or
    computer) that is embedded into some device for some purpose other
    than to provide general purpose computing.  Of course, someone will
    eventually prove you wrong, but who cares?

    A common example of a general purpose computer, would be a typical PC
    clone.  The x86 processor in this machine can't really be considered
    an embedded controller, since the machine is typically used for
    general purpose computing.  However, what is general purpose
    computing?  Take this same PC clone, turn it into a multi-media
    machine, and voila!  You have an appliance - much on the order of a
    microwave oven or television.  Is the x86 processor now considered an
    embedded controller  Or, is the PC clone itself now considered an
    embedded controller, controlling the multi-media peripherals?  Hey -
    I don't know about you, but I'm getting too old for this nonsense.

    Is a microcontroller an embedded processor?  Is an embedded processor
    a microcontroller?  What's the difference between an embedded
    processor and a microcontroller?  Well, today - not much.  With the
    continuing process of high scale integration continuing at a dizzying
    pace, many standard architecture processors are turning up as
    microcontrollers.  A few such examples are the Motorola 68EC300,
    Intel 386 EX, and the IBM PowerPC 403GB.  These chips could be called

    So, what's the difference between an embedded processor and a
    microcontroller?  I wouldn't touch that question with a ten foot
    logic probe.

    We might be safe by stating that an embedded processor controls
    something (for example controlling a device such as a microwave oven,
    car braking system, or a cruise missile).  Is this always true?
    Maybe.  Maybe not.  You know, it just doesn't end.

    The main thing is not to get to hung up on precise definitions.
    Black and white?  Hell no, we've got grey scale, dithering,
    diffusion, you name it!  Same thing goes here with embedded
    controllers, just go with the flow.  It all depends on your point of

    Alright, if you really must insist, we'll take a stab at defining
    what an embedded controller is - realize however that there will be
    many exceptions.  Embedded controllers adhere to a philosophy similar
    to that of microcontrollers, high integration.  By including [many]
    features necessary for the task at hand, an embedded controller
    (processor) can be a powerful yet cost effective solution.  However,
    where a microcontroller [almost by definition] is a computer on a
    chip, an embedded controller might need external components before it
    is considered a "computer."  This is especially true regarding RAM.
    Since including large amounts of RAM (megabytes) on a processor is
    not really practical (due to cost and available silicon real estate)
    and because many embedded controllers are real powerhouses requiring
    large amounts of RAM, the RAM is often external to the processor.

2.3)  Applications

    In addition to the above home monitoring system, embedded processors
    and microcontrollers are frequently found in: appliances (microwave
    oven, refrigerators, television and VCRs, stereos), computers and
    computer equipment (laser printers, modems, disk drives), automobiles
    (engine control, diagnostics, climate control), environmental control
    (greenhouse, factory, home), instrumentation, aerospace, and
    thousands of other uses.  In many items, more than one processor can
    be found.

    Microcontrollers are typically used where processing power isn't so
    important.  Although some of you out there might find a microwave
    oven controlled by a Unix system an attractive idea, controlling a
    microwave oven is easily accomplished with the smallest of
    microcontrollers.  On the other hand, if you're putting together a
    cruise missile to solve the problem of your neighbor's dog barking at
    3 in the morning, you'll probably need to use processors with a bit
    more computing power.

    Embedded processors and microcontrollers are used extensively in
    robotics.  In this application, many specific tasks might be
    distributed among a large number of controllers in one system.
    Communications between each controller and a central, possibly more
    powerful controller (or micro/mini/mainframe) would enable
    information to be processed by the central computer, or to be passed
    around to other controllers in the system.

    A special application that microcontrollers are well suited for is
    data logging.  Stick one of these chips out in the middle of a corn
    field or up in a ballon, and monitor and record environmental
    parameters (temperature, humidity, rain, etc).  Small size, low power
    consumption, and flexibility make these devices ideal for unattended
    data monitoring and recording.

2.4)  Flavors

    Embedded processors come in many flavors and varieties.  Depending on
    the power and features that are needed, you might choose a 4, 8, 16,
    or 32 bit microcontroller.  Standard microprocessors (such as the
    Motorola 68000 or National 32032) are frequently used as powerful
    embedded controllers.  In addition, specialized processors are
    available which include features specific for communications,
    keyboard handling, signal processing, video processing, and other


    Thanks to Robin Getz of National Semiconductor for supplying much of
    the material in this section.

3.1)  Shipments

            WorldWide Microcontroller Shipments (in millions of dollars)

            '90   '91   '92   '93   '94   '95   '96   '97   '98   '99   '00
     4-bit 1,393 1,597 1,596 1,698 1,761 1,826 1,849 1,881 1,856 1,816 1,757
     8-bit 2,077 2,615 2,862 3,703 4,689 5,634 6,553 7,529 8,423 9,219 9,715
    16-bit   192   303   340   484   810 1,170 1,628 2,191 2,969 3,678 4,405

                 WorldWide Microcontroller Shipments (in Millions)

             '90   '91   '92   '93   '94   '95   '96   '97   '98   '99   '00
     4-bit   778   906   979  1036  1063  1110  1100  1096  1064  1025   970
     8-bit   588   753   843  1073  1449  1803  2123  2374  2556  2681  2700
    16-bit    22    38    45    59   106   157   227   313   419   501   585

                                                   Source: WSTS & ICE - 1994

    If you were wondering why you should bother learning about
    microcontrollers - well, the tables above should fairly scream the
    answer at you.  Microcontrollers will be *BIG* business - we're
    talking piles of cash - billions!

    Notice that even the lowly 4-bit device is holding its own - what use
    is a 16-bit part in a toaster oven?  Also notice that the 8-bit
    market just keeps growing, and will probably continue to grow.  8-bit
    devices account for over half of the market, and will eventually grab
    even more.  Now do you understand why every silicon manufacturer is
    really pushing their 8-bit microcontrollers?

3.2)  Industrial applications

    Average Semiconductor Content per Passenger Automobile (in Dollars)

        '90   '91   '92   '93   '94   '95   '96   '97   '98   '99   '00
     $  595   634   712   905 1,068 1,237 1,339 1,410 1,574 1,852 2,126

                                                     Source: ICE - 1994

    The automotive market is the most important single driving force in
    the microcontroller market, especially at it's high end.  Several
    microcontroller families were developed specifically for automotive
    applications and were subsequently modified to serve other embedded

    The automotive market is demanding.  Electronics must operate under
    extreme temperatures and be able to withstand vibration, shock, and
    EMI.  The electronics must be reliable, because a failure that causes
    an accident can (and does) result in multi-million dollar lawsuits.
    Reliability standards are high - but because these electronics also
    compete in the consumer market - they have a low price tag.

    Automotive is not the only market that is growing.  DataQuest says
    that in the average North American's home there are 35
    microcontrollers.  By the year 2000 - that number will grow to 240.
    Consumer electronics is a booming business.

3.3)  Deciding whose microcontroller to use

    When deciding which devices to implement in a design, there are lots
    of things to consider besides who else is using these devices (and
    how many are they using).
      - Can I expect help when I am having problems?
      - What development tools are available and how much do they cost?
      - What sort of documentation is available (reference manuals,
        application notes, books)?
      - Can I work a deal by purchasing more devices at one manufacturer?
        That is, purchasing not only the microcontroller, but also
        peripherals (A/D, memory, voltage regulator, etc.) from one
      - Do they support OTPs, windowed devices, mask parts?

3.4)  The players

       Rank                   Sales ($ millions)
    1995  1994   Company        1995      1994
      1     1    Intel       $10,800    $8,036
      2     3    AMD             881       992
      3     2    Motorola        781       827
      4    11    IBM             468       297
      5     6    TI              219       202
      6     4    Cyrix           210       240
      7     5    Hitachi         188        66
      8     7    NEC             100        82
      9     8    LSI Logic        58        51
     10    10    IDT              45        25

                                        Source: In-Stat Inc.

       Rank                     Sales ($ millions)
    1995  1994   Company          1995      1994
      1     1    Motorola       $1,781    $1,511
      2     2    NEC             1,421     1,208
      3     4    Mitsibishi        945       708
      4     3    Hitachi           899       782
      5     5    Intel             835       605
      6     6    TI                807       534
      7     8    Philips           524       345
      8     7    Matsushita        500       413
      9    10    Lucent (AT&T)     492       275
     10     9    Toshiba           400       328

                                        Source: In-Stat Inc.


    Thanks to Robin Getz of National Semiconductor who supplied some of
    the material in this section.

4.1)  Fabrication techniques

    CMOS - Complementary Metal Oxide Semiconductor

       This is the name of a common technique used to fabricate most (if
       not all) of the newer microcontrollers.  CMOS requires much less
       power than older fabrication techniques, which permits battery
       operation.  CMOS chips also can be fully or near fully static,
       which means that the clock can be slowed up (or even stopped)
       putting the chip in sleep mode.  CMOS has a much higher immunity
       to noise (power fluctuations or spikes) than the older fabrication

    PMP - Post Metal Programming (National Semiconductor)

       PMP is a high-energy implantation process that allows
       microcontroller ROM to be programmed AFTER final metalization.
       Usually ROM is implemented in the second layer die, with nine or
       ten other layers then added on top.  That means the ROM pattern
       must be specified early in the production process, and completed
       prototypes devices won't be available typically for six to eight
       weeks.  With PMP, however, dies can be fully manufactured through
       metalization and electrical tests (only the passivation layers
       need to be added), and held in inventory.  This means that ROM can
       be programmed late in production cycle, making prototypes
       available in only two weeks.

4.2)  Architectural features

    Von-Neuman Architecure

       Microcontrollers based on the Von-Neuman architecture have a
       single "data" bus that is used to fetch both instructions and
       data.  Program instructions and data are stored in a common main
       memory.  When such a controller addresses main memory, it first
       fetches an instruction, and then it fetches the data to support
       the instruction.  The two separate fetches slows up the
       controller's operation.

    Harvard Architecture

       Microcontrollers based on the Harvard Architecture have separate
       data bus and an instruction bus.  This allows execution to occur
       in parallel.  As an instruction is being "pre-fetched", the
       current instruction is executing on the data bus.  Once the
       current instruction is complete, the next instruction is ready to
       go.  This pre-fetch theoretically allows for much faster execution
       than a Von-Neuman architecture, but there is some added silicon


       Almost all of today's microcontrollers are based on the CISC
       (Complex Instruction Set Computer) concept.  The typical CISC
       microcontroller has well over 80 instructions, many of them very
       powerful and very specialized for specific control tasks.  It is
       quite common for the instructions to all behave quite differently.
       Some might only operate on certain address spaces or registers,
       and others might only recognize certain addressing modes.

       The advantages of the CISC architecture is that many of the
       instructions are macro-like, allowing the programmer to use one
       instruction in place of many simpler instructions.


       The industry trend for microprocessor design is for Reduced
       Instruction Set Computers (RISC) designs.  This is beginning to
       spill over into the microntroller market.  By implementing fewer
       instructions, the chip designed is able to dedicate some of the
       precious silicon real-estate for performance enhancing features.
       The benefits of RISC design simplicity are a smaller chip, smaller
       pin count, and very low power consumption.

       Among some of the typical features of a RISC processor:
          - Harvard architecture (separate buses for instructions and
            data) allows simultaneous access of program and data, and
            overlapping of some operations for increased processing
          - Instruction pipelining increases execution speed
          - Orthogonal (symmetrical) instruction set for programming
            simplicity; allows each instruction to operate on any
            register or use any addressing mode; instructions have no
            special combinations, exceptions, restrictions, or side


       Actually, a microcontroller is by definition a Reduced Instruction
       Set Computer (at least in my opinion).  It could really be called
       a Specific Instruction Set Computer (SISC).  The [original] idea
       behind the microcontroller was to limit the capabilities of the
       CPU itself, allowing a complete computer (memory, I/O, interrupts,
       etc) to fit on the available real estate.  At the expense of the
       more general purpose instructions that make the standard
       microprocessors (8088, 68000, 32032) so easy to use, the
       instruction set was designed for the specific purpose of control
       (powerful bit manipulation, easy and efficient I/O, and so on).

       Microcontrollers now come with a mind boggling array of features
       that aid the control engineer - watchdog timers, sleep/wakeup
       modes, power management, powerful I/O channels, and so on.  By
       keeping the instruction set specific (and reduced), and thus
       saving valuable real estate, more and more of these features can
       be added, while maintaining the economy of the microcontroller.

4.3)  Advanced Memory options

    EEPROM - Electrically Erasable Programmable Read Only Memory

       Many microcontrollers have limited amounts of EEPROM on the chip.
       EEPROM seems more suited (becuase of its economics) for small
       amounts of memory that hold a limited number of parameters that
       may have to be changed from time to time.  This type of memory is
       relatively slow, and the number of erase/write cycles allowed in
       its lifetime is limited.


       Flash provides a better solution than regular EEPROM when there is
       a requirement for large amounts of non-volatile program memory.
       It is both faster and permits more erase/write cycles than EEPROM.

    Battery backed-up static RAM

       Battery backed-up static RAM is useful when a large non-volatile
       program and DATA space is required.  A major advantage of static
       RAM is that it is much faster than other types of non-volatile
       memory so it is well suited for high performance application.
       There also are no limits as to the number of times that it may be
       written to so it is perfect for applications that keep and
       manipulate large amounts of data locally.

    Field programming/reprogramming

       Using nonvolatile memory as a place to store program memory allows
       the device to be reprogrammed in the field without removing the
       microcontroller from the system that it controls.  One such
       application is in automotive engine controllers.  Reprogrammable
       non-volatile program memory on the engine's microcontroller allows
       the engine controller program to be modified during routine
       service to incorporate the latest features or to compensate for
       such factors as engine aging and changing emissions control laws
       (or even to fix bugs!!).  Reprogramming of the microcontroller
       could become a standard part the routine engine tune-up.

       Almost every application could benefit from this type of program
       memory - If a modem's hardware supported it, you could remotely
       upgrade your modem from Vfast to V.34, or incorporate new features
       such as voice control or a digital answering machine.

    OTP - One Time Programmable

       An OTP is a PROM (Programmable Read-Only-Memory) device.  Once
       your program is written into the device with a standard EPROM
       programmer, it can not be erased or modified.  This is usually
       used for limited production runs before a ROM mask is done in
       order to test code.

       A OTP (One Time Programmable) part uses standard EPROM, but the
       package has no window for erasing.  Once your program is written
       into the device with a standard EPROM programmer, it cannot be
       erased or modified.  (Well, sort of - any bit that is a one can be
       changed to a zero - but a bit that is a zero cannot be changed
       into a one).

       As product design cycles get shorter, it is more important for
       micro manufacturers to offer OTPs as an option.  This was commonly
       used for limited production runs before a ROM mask in order to
       test code.  However, one problem with Mask ROM is that
       programming, setup, and engineering charges make it economical
       only when the systems manufacturer purchases large quantities of
       identically programmed micros.  Then when you discover THAT bug
       (and find it and fix your code), you have quantities of *old
       buggy* micros around that you have to throw away.  Not to mention
       that lead time (the time when you submit your code to the micro
       manufacture, to the time you receive your micro with your code on
       it) can be at least 8 weeks, and as bad as 44 weeks.

    Software protection

       Either by encryption or fuse protection, the programmed software
       is protected against unauthorized snooping (reverse engineering,
       modifications, piracy, etc.).

       This is only an option on OTPs and Windowed devices.  On Masked
       ROM devices, security is not needed - the only way to read your
       code would be to rip the microcontroller apart with a scanning
       electron microscope - and how many people really have one of

       Although - and this is a manufacturer's little know fact - when a
       silicon manufacturer makes your ROMed microcontroller - they have
       to test it in order to make sure that it is programmed properly.
       (You should see what a spec of dust does on a mask :-)  In order
       to test this, they must be able to read out the ROM and compare it
       to the code you submitted.  This mode is known as test mode.  IN
       tells you different, does not know what they are talking about -
       or is lying.  This is usually not a big deal because test mode is
       ***VERY*** confidential, and (usually) only known by that
       manufacturer (i.e. you cannot put a device into test mode by
       accident).  Test mode is ONLY applicable with ROMed devices.

4.4)  Power Management and Low Voltage

    Low voltage parts

       Since automotive applications have been the driving force behind
       most microcontrollers, and 5 Volts is very easy to do in a car,
       most microcontrollers have only supported 4.5 - 5.5 V operation.
       In the recent past, as consumer goods are beginning to drive major
       segments of the microcontroller market, and as consumer goods
       become portable and lightweight, the requirement for 3 volt (and
       lower) microcontrollers has become urgent (3 volts = 2 battery
       solution / lower voltage = longer battery life).  Most low voltage
       parts in the market today are simply 5 volt parts that were
       modified to operate at 3 volts (usually at a performance loss).
       Some micros being released now are designed from the ground up to
       operate properly at 3.0 (and lower) voltages, which offer
       comparable performance of the 5 volt devices.

       Now, why are voltages REALLY going down on ICs?  Paul K. Johnson
       (of Hewlett-Packard) explains:

       There are a few interesting rules of thumb regarding transistors:
       1)  The amount of power they dissipate is proportional to their
           size.  If you make a transistor half as big, it dissipates
           half as much power.
       2)  Their propagation delay is proportional to their size.  If you
           make a transistor half as big, it's twice as fast.
       3)  Their cost is proportional to the square of their size.  If
           you make them half as big, they cost one quarter as much.

       If you make a transistor smaller, you improve the power, speed,
       and cost.  The only drawback is that they are harder to make.
       (Hey, how hard can it be for HP, IBM, Motorola, National, etc?
       ed.)  Everybody in the world wants to make transistors smaller and
       smaller, the advantages are enormous.

       For years people have been using 5 Volts to power IC's.  Because
       the transistors were large, there was little danger damaging the
       transistor putting this voltage across it.  However, now that the
       transistors are getting so small, 5 Volts will actually fry them.
       The only way around this is to start lowering the voltage.  This
       is why people are now using 3 (actually 3.3) Volt logic, and lower
       in the next few years.  It isn't just because of batteries.

    Brownout Protection

       Brownout protection is usually an on-board protection circuit that
       resets the device when the operating voltage (Vcc) is lower than
       the brownout voltage.  The device is held in reset and will remain
       in reset when Vcc stays below the Brownout voltage.  The device
       will resume execution (from reset) after Vcc has risen above the
       brownout Voltage.


       The device can be placed into IDLE/HALT mode by software control.
       In both Halt and Idle conditions the state of the microcontroller
       remains.  RAM is not cleared and any outputs are not changed.  The
       terms idle and halt often have different definitions, depending on
       the manufacturer.  What some call idle, others may call halt, and
       vice versa.  It can be confusing, so check the data sheet for the
       device in question to be sure.

       In IDLE mode, all activities are stopped except:
         - associated on-board oscillator circuitry
         - watchdog logic (if any)
         - the clock monitor
         - the idle timer (a free running timer)
       Power supply requirements on the microcontroller in this mode are
       typically around 30% of normal power requirements of the
       microprocessor.  Idle mode is exited by a reset, or some other
       stimulus (such as timer interrupt, serial port, etc.).  A special
       timer/counter (the idle timer) causes the chip to wake up at a
       regular interval to check if things are OK.  The chip then goes
       back to sleep.

       IDLE mode is extremely useful for remote, unattended data logging
       - the microprocessor wakes up at regular intervals, takes its
       measurements, logs the data, and then goes back to sleep.

       In Halt mode, all activities are stopped (including timers and
       counters).  The only way to wake up is by a reset or device
       interrupt (such as an I/O port).  The power requirements of the
       device are minimal and the applied voltage (Vcc) can sometimes be
       decreased below operating voltage without altering the state
       (RAM/Outputs) of the device.  Current consumption is typically
       less than 1 uA.

       A common application of HALT mode is in laptop keyboards.  In
       order to have maximum power saving, the controller is in halt
       until it detects a keystroke (via a device interrupt).  It then
       wakes up, decodes and sends the keystroke to the host, and then
       goes back into halt mode, waiting either for another keystroke, or
       information from the host.

    Multi-Input Wakeup (National Semiconductor)

       The Multi-Input WakeUp (MIWU) feature is used to return (wakeup)
       the microcontroller from either HALT or IDLE modes.  Alternately
       MIWU may also be used to generate up to 8 edge selectible external
       interrupts.  The user can select whether the trigger condition on
       the pins is going to be either a positive edge (low to high) or a
       negative edge (high to low).

4.5)  I/O


       A UART (Universal Asynchronous Receiver Transmitter) is a serial
       port adapter for asynchronous serial communications.


       A USART (Universal Synchronous/Asynchronous Receiver Transmitter)
       is a serial port adapter for either asynchronous or synchronous
       serial communications.  Communications using a USART are typically
       much faster (as much as 16 times) than with a UART.

    Synchronous serial port

       A synchronous serial port doesn't require start/stop bits and can
       operate at much higher clock rates than an asynchronous serial
       port.  Used to communicate with high speed devices such as memory
       servers, display drivers, additional A/D ports, etc.  Can also be
       used to implement a simple microcontroller network.

    SPI (Motorola)

       An SPI (serial peripheral interface) is a synchronous serial port.


       An SCI (serial communications interface) is an enhanced UART
       (asynchronous serial port).

    I2C bus - Inter-Integrated Circuit bus (Philips)

       The I2C bus is a simple 2 wire serial interface developed by
       Philips.  It was developed for 8 bit applications and is widely
       used in consumer electronics, automotive and industrial
       applications.  In addition to microcontrollers, several
       peripherals also exist that support the I2C bus.

       The I2C bus is a two line, multi-master, multi-slave network
       interface with collision detection.  Up to 128 devices can exist
       on the network and they can be spread out over 10 meters.  Each
       node (microcontroller or peripheral) may initiate a message, and
       then transmit or receive data.  The two lines of the network
       consist of the serial data line and the serial clock line.  Each
       node on the network has a unique address which accompanies any
       message passed between nodes.  Since only 2 wires are needed, it
       is easy to interconnect a number of devices.

    MICROWIRE/PLUS (National Semiconductor)

       MICROWIRE/PLUS is a serial synchronous bi-directional
       communications interface.  This is used on National Semiconductor
       Corporation's devices (microcontrollers, A/D converters, display
       drivers, EEPROMS, etc.).

    CAN & J1850

       CAN (Controller Area Network) is a mutiplexed wiring scheme that
       was developed jointly by Bosh and Intel for wiring in automobiles.
       J1850 is the SAE (Society of Automotive Engineers) multiplexed
       automotive wiring standard that is currently in use in North

       Both of these groups have the "NOT INVENTED HERE" syndrome and
       refuse to work with each other's standard. The standards are quite
       different and are not compatible at all.

       The CAN specification seems to be the one that is being used in
       industrial control both in North American and Europe.  With lower
       cost microcontrollers that support CAN, CAN has a good potential
       to take off.

       Ken Tindell points out that although the J1850 and CAN buses are
       incompatible at an electrical level, they are almost the same at a
       higher level. They both use short-frame priority arbitration based
       on 29-bit identifiers. At a software-level there is hope. Isn't
       there always?

    Analog to Digital Conversion (A/D)

       Converts an external analog signal (typically relative to voltage)
       and converts it to a digital representation.  Microcontrollers
       that have this feature can be used for instrumention,
       environmental data logging, or any application that lives in an
       analog world.

       The various types of A/D converters that can be found:

       Succesive Approximation A/D converters -- This the most common
       type of A/D and is used in the majority of microcontrollers.  In
       this technique, the converter figures out each bit at a time (most
       significant first) and finds if the next step is higher or lower.
       This way has some benefits - it takes exactly the same amount of
       time for any conversion - it is very common - (and therefore very
       cheap).  However it also has some disadvantages - it is slow - for
       every bit it takes at least one clock cycle - the best an 8-bit
       A/D can do is at least 8 clock cycles (and a couple for
       housekeeping).  Because it takes so long - it is a power hog as
       compared to the other types of A/Ds.

       Single Slope A/D converters -- This is the type of converter that
       you can build yourself (if the microcontroller has a couple of
       analog blocks on it).  Your single slope A/D converter would
       include Analog Mux / comparator / timer (8-bit timer = 8 bit A/D -
       16-bit timer = 16 bit A/D) with input capture and a constant
       current source.  The only microcontroller (that I know of) that
       has all of this on it is National's COP888EK.

       First Step is to clear the timer to 0000 and then start it.  It is
       a simple matter to hang an external capacitor, and charge it with
       the constant current source (linearly because of the current
       source) when the voltage on the cap exceeds the sampling voltage,
       the comparitor toggles, stops the timer - and voila - you have the
       voltage in uSecs - with 16-bit accuracy.  The only drawback is you
       can't really expect 16 bits (14 yes) - the conversion time varies
       quite a bit, and it is SLOW.

       Delta-Sigma A/Ds converters -- This type of A/D converter is found
       on higher-end DSPs.  These are the hardest to understand of the
       A/Ds because it just makes a best guess (a little National
       Semiconductor humor here :-).  Delta sigma A/Ds can be broken down
       into two main parts.

       The modulator which does the A/D conversion and the filter, which
       turns the output of the modulator into a format suitible for the
       microcontroller (or DSP).

       The modulator is very simple - it just compares the input voltage
       to the average of the last 100 (or so) modulator outputs and
       decides if the input is higher or lower than the average. This
       happens millions of times a second, resulting in a high speed
       single-bit datastream of 1s and 0s who's *average* is equal to the
       input voltage. Becuse the ouput is only a one or a zero, there are
       very few sources of errors. This is the main reason that
       delta-sigma A/Ds are **very** accurate.

       The filter comes after the modulator ... and this filter is
       essentially a big DSP block.  It must take the very high speed
       stream of ones and zeros and turn it into a slower speed stream of
       16-bit (or greater) words to be used by the microcontroller.  This
       process is called decimation and the filter is often called a
       "comb filter".  Another digital filter follows this stage and
       rejects unwanted frequencies.  This filter performs a similar
       function to the anti-aliasing filter required in many traditional
       A/D appliactions, but it does it at an unprecedented level of
       performance and at low cost.  This is the other major benefit of
       delta-sigma A/Ds.

       Flash A/D -- This is the basic architecure for the fastest
       category of A/Ds.  The flash converter involves looking at each
       level that is possible and instantaneously saying what level the
       voltage is at.  This is done by setting up comparators as
       threshold detectors with each detector being set up for a voltage
       exaclty 1 LSB higher than the detector below it.  The benefit of
       this architecture is that with a single clock cycle, you can tell
       exactly what the input voltage is - that is why it is so fast.
       The disadvantage is that to achieve 8-bit accuracy you need 256
       comparators and to achieve 10-bit accuracy you need 1024
       comparators. To make these comparators operate at higher speeds,
       they have to draw LOTS of current, and beyond 10 bits, the number
       of comparators required becomes totally unmanageable.

    D/A (Digital to Analog) Converters

       This feature takes a Digital number and converts it to a analog
       output. The number 50 would be changed to the analog output of
       (50/256 * 5Volts) = .9765625V on a 8-bit / 5 Volt system.

    Pulse width modulator

       Often used as a digital-to-analog conversion technique.  A pulse
       train is generated and regulated with a low-pass filter to
       generate a voltage proportional to the duty cycle.

    Pulse accumulator

       A pulse accumulator is an event counter.  Each pulse increments
       the pulse accumulator register, recording the number of times this
       event has occurred.

    Input Capture

       Input Capture can measure external frequencies or time intervals
       by copying the value from a free running timer into a register
       when an external event occurs.


       One or more standard comparators can sometimes be placed on a
       microcontroller die.  These comparators operate much like standard
       comparators however the input and output signals are available on
       the microcontroller bus.

    Mixed (Analog-Digital) Signal

       We live in an analog world where the information we see, hear,
       process, and exchange with each other, and with our mechanical and
       electronic systems, is always an analog quantity - pressure,
       temperature, voltage, current, air and water flow are always
       analog entities.  They can be digitized for more efficient
       sorting, storage and transmittal, but the interface - the input
       and output - is almost always analog.  Thus the essence of analog
       electronics lies in sensing continuously varying information,
       shaping and converting it for the efficiency of digital processing
       and transmission, and reshaping the digital data to an analog
       signal at the other end.

       Mixed analog-digital devices are being used increasingly to
       integrate the complex functions of high-speed telecommunications,
       or the real-time data processing demanded by industrial control
       systems and automotive systems.  Start looking for
       microcontrollers that have analog comparators, analog
       multiplexers, current sources, voltage doublers, PLL (Phase Lock
       Loops) and all sorts of peripherals that you thought were analog

4.6)  Interrupts


       Polling is not really a "feature" - it's what you have to do if
       your microcontroller of choice does not have interrupts.
       Polling is a software technique whereby the controller continually
       asks a peripheral if it needs servicing.  The peripheral sets a
       flag when it has data ready for transferring to the controller,
       which the controller notices on its next poll.  Several such
       peripherals can be polled in succession, with the controller
       jumping to different software routines, depending on which flags
       have been set.


       Rather than have the microcontroller continually polling - that
       is, asking peripherals (timers / UARTS / A/Ds / external
       components) whether they have any data available (and finding most
       of the time they do not), a more efficient method is to have the
       peripherals tell the controller when they have data ready.  The
       controller can be carrying out its normal function, only
       responding to peripherals when there is data to respond to.  On
       receipt of an interrupt, the controller suspends its current
       operation, identifies the interrupting peripheral, then jumps
       (vectors) to the appropriate interrupt service routine.

       The advantage of interrupts, compared with polling, is the speed
       of response to external events and reduced software overhead (of
       continually asking peripherals if they have any data ready).

       Most microcontrollers have at least one external interrupt, which
       can be edge selectible (rising or falling) or level triggered.
       Both systems (edge/level) have advantages.  Edge - is not time
       sensitive, but it is susceptible to gitches.  Level - must be held
       high (or low) for a specific duration (which can be a pain - but
       is not susceptible to glitches).

       Interrupts are critical when you are controlling anything (this is
       what microcontrollers do).  If you misunderstand any of the terms,
       and design your systems with the way you *think* it works - not
       the way it *really* works - it will effect system performance.  It
       may also work for a very long time with no problems, and then all
       of a sudden fail.  Check your datasheets - these descriptions are
       the correct ones (or are at least supposed to be), but that does
       not mean that they are agreed to by the silicon manufacturers, (or
       by the marketing guys that they employ, and who write parts of the
       data sheets.)

       4 bit microcontrollers usually have either a polling or
       non-vectored type of interrupt scheme.  8 and 16 bit
       microcontrollers usually have some type of vectored arbitration
       type of interrupt scheme.  32 bit microcontrollers usually will
       have some type of vectored priority type of interrupt scheme.
       Again, check your data sheet to make sure - or ask a
       manufacturer's rep if you aren't sure.

    Maskable Interrupts

       A maskable interrupt is one that you can disable or enable
       (masking it out means disabling the interrupt), whereas
       non-maskable interrupts you can't disable.  The benefit of
       maskable interrupts is that you can turn off a particular
       interrupts (for example a UART) during some time critical task.
       Then, those particular interrupts will be ignored thus allowing
       the microcontroller to deal with the task at hand.  Most
       microcontrollers (as well as most microprocessors) have some type
       of Global Interrupt Enable (GIE) which allows you to turn off (or
       on) all of the maskable interrupts with one bit.  NOTE:  GIE
       usually does not effect any NMI (Non-Maskable Interrupts)

    Vectored Interrupts

       Simple (non-vectored) interrupts is one of the simplest interrupt
       schemes there is (Simple = less silicon = more software = slower).
       Whenever there is an interrupt, the program counter (PC) branches
       to one specific address.  At this address, the system designer
       needs to check the interrupts (one at a time) to see which
       peripheral has caused the interrupt to occur.  Code for this may
       look like (on a COP8):

         IFBIT  UART,PSW      ; If the UART bit has been set
         JP     UART_Recieve  ;  Jump to the UART receive service routine

         IFBIT  T1,PSW        ; If the timer has underflowed
         JP     Underflow     ;  Jump to the underflow service routine

         ...   and so on

       This can be *very* slow - and the time between the interrupt
       happening and the time the service routine is entered, depends on
       how the system designer sets up their ranking.  The peripheral
       that is checked last takes the longest to process.  Most
       microcontrollers that have fewer than 3 - 5 interrupts use this
       method.  The benefit of this is that the system designer can set
       the priority - The most important peripheral gets checked first -
       and you get to decide which peripheral that is.

       Vectored interrupts are a little easier to set up, but the system
       designer has less control of the system (i.e. is dependent on the
       silicon manufacture to make the proper decisions during design of
       the chip).  When an interrupt occurs, the hardware interrupt
       handler automatically branches to a specific address depending on
       what interrupt occurred.  This is much faster than the
       non-vectored approach described above, however the system designer
       does not get to decide what peripheral gets checked first.
       Example (on a National Semiconductor COP888CG):

          Rank         Source          Description        Vector Address
            1 (highest) Software       INTR Instruction    01FE - 01FF
            2           External       Pin G0 Edge         01FA - 01FB
            3           Timer T0       Underflow           01F8 - 01F9
            4           Timer T1       T1A / Underflow     01F6 - 01F7
            5           Timer T1       T1B                 01F4 - 01F5
            6           MICROWIRE/PLUS BUSY Goes Low       01F2 - 01F3
            7           UART           Receive             01EE - 01EF
            8           UART           Transmit            01EC - 01ED
            9           Timer T2       T2A / Underflow     01EA - 01EB
           10           Timer T2       T2B                 01E8 - 01E9
           11           Timer T3       T3A / Underflow     01E6 - 01E7
           12           Timer T3       T3B                 01E4 - 01E5
           13           Port L / MIWU  Port L Edge         01E2 - 01E3
           14 (lowest)  Default        VIS Interaction     01E0 - 01E1

       In ROM location 01F8 - 01F9 (2bytes x 8 bits = 16bit address) the
       system designer enters the ROM location of where they want the
       service routine (of the Timer T0 underflow) to be. And so on for
       the rest of the addresses.

    Interrupt arbitration and priority

       Interrupt arbitration and priority - These are two of the most
       misused words when it comes to microcontrollers (microprocessors
       too for that matter) and it's generally because no one knows the
       difference between them.  Priority is not Arbitration.
       Arbitration is not Priority.  Lets see if we can sort out the

       Arbitration - If you look at the above chart of the COP888CG, you
       may think the interrupts are prioritized because they have some
       ranking.  They do have rank, but they are not prioritized.  What
       happens is that (in an arbitration scheme) when an interrupt
       occurs, the GIE (Global Interrupt Enable) is cleared.  This
       effectively means that all future interrupts will be delayed until
       the GIE is set.  The GIE becomes set only if the system designer
       sets it in a service routines, or on a RETI (Return from

       Quick Example 1 - Timer 1 underflows - the hardware clears the
       GIE, looks at ROM locations 01F6 and 01F7 and jumps to the ROM
       location pointed to by those addresses.  The program does a couple
       things, and then sets the GIE (because the user wants to recognize
       an external interrupt during this service routine).  However while
       in the service routine, Timer 3 underflows.  Although a timer 3
       underflow is lower in rank than a timer 1 underflow, the interrupt
       handler does not care - it simply looks at the GIE, and because it
       is set - handles the interrupt (now we have nested interrupts).
       The Timer 1 underflow service routine will not be completed until
       the Timer 3 underflow is complete.

       Quick Example 2 - Timer 3 underflows at the same time as an
       External interrupt occur.  The one to be handled first is the
       External Interrupt.  If the user sets the GIE, the interrupt
       handler will jump down to the Timer 3 underflow handler.  If the
       user does not set the GIE, the microcontroller handles the
       External interrupt, does a RETI, and the Timer 3 underflow can now
       be handled.

       Priority - In a priority scheme, things are prioritized (well,
       what'd you expect?).  If Timer T0 underflows, the only thing that
       can interrupt that is an external or software interrupt.  If a
       external or software interrupt occurs, the interrupt handler will
       branch to these service routines.  When they are complete, it will
       return to the Timer T0 underflow.

       Quick Example - In the below timing diagram, the following
         1) Timer T0 underflows
         2) Timer T2 underflows
         3) An External Interrupt occurs.

       In a priority scheme, the following would happen:

        External Interrupt             |---------|
                                       |         |
        Timer T0 Underflow     |-------|         |------|
                               |                        |
        Timer T2 Underflow     |                        |------|
                               |                               |
        Normal Execution    ---|                               |-------

                               ^   ^   ^         ^      ^       ^
                               |   |   |         |      |       |
        Time ->                |   |   |         |      |       \-T2 Done
                               |   |   |         |      \-------- T0 Done
                               |   |   |         \-------------- Ext Done
                               |   |   \------------------------ Ext Edge
                               |   \----------------------- T2 Underflows
                               \--------------------------- T0 Underflows

       This is what RTOS (Real Timer Operating Systems) do - prioritize
       and handle interrupts.

4.7)  Special microcontroller features

    Watchdog timer

       A watchdog timer provides a means of graceful recovery from a
       system problem.  This could be a program that goes into an endless
       loop, or a hardware problem that prevents the program from
       operating correctly.  If the program fails to reset the watchdog
       at some predetermined interval, a hardware reset will be
       initiated.  The bug may still exist, but at least the system has a
       way to recover.  This is especially useful for unattended systems.

    Digital Signal Processors (DSP)

       Microcontrollers react to and control events - DSPs execute
       repetitive math-intensive algorithms.  Today many embedded
       applications require both types of processors, and semiconductor
       manufacturers have responded by introducing microcontrollers with
       on-chip DSP capability and DSPs with on-chip microcontrollers.

       The most basic thing a DSP will do is a MACC (Multiply and
       ACCumulate).  The number of data bits a DSP can Multiply and
       ACCumulate will determine the dynamic range (and therefore the

        Bits Fixed/Floating  Dynamic Range   Typical Application

          8     Fixed           48 dB         Telephone-quality voice
         16     Fixed           96 dB         Compact disk (marginal)
         24     Fixed          144 dB         Compact disk
                                                  (room for error)

    Clock Monitor

       A clock monitor can shut the microcontroller down (by holding the
       microcontroller in reset) if the input clock is too slow.  This
       can usually be turned on or off under software control.

    Resident program loader

       Loads a program by Initializing program/data memory from either a
       serial or parallel port.  Convenient for prototyping or trying out
       new features, eliminates the erase/burn/program cycle typical with
       EPROMs, and allows convenient updating of a system even from an
       offsite location.


       A monitor is a program installed in the microcontroller which
       provides basic development and debug capabilities.  Typical
       capabilities of a microcontroller monitor include:  loading object
       files into system RAM, executing programs, examining and modifying
       memory and registers, code disassembly, setting breakpoints, and
       single-stepping through code.  Some simple monitors only allow
       basic functions such as memory inspection, and the more
       sophisticated monitors are capable of a full range of debug

       Monitors can either communicate with a dumb terminal or with a
       host computer such as a PC.  Much of the work of the monitor (such
       as user interface) can be offloaded to the host PC running a
       program designed to work with the monitor.  This makes it possible
       to reduce the size and complexity of the code that must be
       installed in the target system.

    MIL transducer

       An MIL transducer is a sophisticated and expensive device that
       detects the presence of your mother-in-law.  Sensitivity settings
       are possible for a full range of stimuli such as:  snarling,
       stomping, nasty faces, and others.  Techno-Wimp (address withheld
       upon request), the sole manufacturer of the MIL transducer, has
       recently announced a major new version which is sensitive enough
       to detect less-tangible stimuli.  This breakthrough product is
       dubbed the MIL-WOMF ("Whoa, outta my face!") transducer.  Both the
       original MIL and the new MIL-WOMF transducers are programmable and
       easy to interface to most microcontrollers.

5)  Some popular microcontrollers

    Some common microcontrollers are described below.  A common question
    is "what microcontroller should I use for...?"  Well, that's a tough
    one.  The best advice would be to choose a chip that has a full set
    of development tools at the price you can afford, and good
    documentation.  For the hobbyist, the Intel 8051, Motorola 68hc11, or
    Microchip PIC would all make suitable choices.

    8048 (Intel)

       The grandaddy of 'em all, the first microcontroller, it all
       started here!  Although a bit long in the tooth and a bit kludgey
       in design (at least by today's standards), it is still very
       popular due to its very low cost, availability, and wide range of
       development tools.

       Modified Harvard architecture with program ROM on chip with an
       additional 64 to 256 bytes of RAM also on chip.  I/O is mapped in
       its own space.

    8051 (Intel and others)

       The 8051, Intel's second generation of microcontrollers, rules the
       microcontroller market at the present time.  Although featuring a
       somewhat bizarre design, it is a very powerful and easy to program
       chip (once you get used to it).

       Modified Harvard architecture with separate address spaces for
       program memory and data memory.  The program memory can be up to
       64K.  The lower portion (4K or 8K depending on type) may reside on
       chip.  The 8051 can address up to 64K of external data memory, and
       is accessed only by indirect addressing.  The 8051 has 128 bytes
       (256 bytes for the 8052) of on-chip RAM, plus a number of special
       function registers (SFRs).  I/O is mapped in its own space.

       The 8051 features the so-called "boolean processor".  This refers
       to the way instructions can single out bits just about anywhere
       (RAM, accumulators, I/O registers, etc.), perform complex bit
       tests and comparisons, and then execute relative jumps based on
       the results.

       Piles of software, both commercial and free, are available for the
       8051 line.  Many manufacturers supply what must be a hundred
       different variants of this chip for any requirement.  Often
       featured in construction projects in the popular hobbyist

    80c196 (MCS-96)

       The third generation of Intel microprocessors, the 80c196 is a 16
       bit processor.  Originally fabricated in NMOS (8096), it is now
       mainly available in CMOS.  Intel Corp. has recently introduced a
       clock-doubled (50MHz) version of the 80c196.

       Among the many features it includes are: hardware multiply and
       divide, 6 addressing modes, high speed I/O, A/D, serial
       communications channel, up to 40 I/O ports, 8 source priority
       interrupt controller, PWM generator, and watchdog timer.

    80186,80188 (Intel)

       These chips are, in essence, microcontroller versions of the 8086
       and 8088 (of IBM/PC fame).  Included on the chip are: 2 channels
       of DMA, 2 counter/timers, programmable interrupt controller, and
       dynamic RAM refresh.  There are several variations including:  low
       power versions, variations with serial ports, and so on.

       One major advantage you gain by using one of these parts is that
       you can use standard PC development tools (compilers, assemblers,
       etc) for developing you applications.  If you are already familiar
       with PC software development, the learning curve will be short,
       since these chips have the same basic architecture as the original
       8088 (as used in the IBM/PC).

       Other advantages include high speed processing, a full megabyte
       addressing space, and powerful interrupt processing.

    80386 EX (Intel)

       The 80386 EX is of course a 386 in microcontroller clothing.
       Included on the chip are: serial I/O, power management, DMA,
       counter/timers, programmable interrupt controller, and dynamic RAM
       refresh.  And of course, all of the power of the 386

       One major advantage you gain by using one of these parts is that
       you can use standard PC development tools (compilers, assemblers,
       etc) for developing your applications.  If you are already
       familiar with PC software development, the learning curve will be
       short, since these chips have the same basic architecture as the
       original 8088 (as used in the IBM/PC).

       We're talking power here gang.  Now let's all wait for Microsoft
       to release a version of Windows for embedded and real-time
       applications (Windows ET?  Windows RT?  Windows 2000? :-).

    65C02/W65C816S/W65C134S (Western Design Center)

       The Western Design Center, Inc. is the original owner and designer
       of the 65C02 8-bit microprocessor, used in the original Apple,
       Commodore, and Atari computers. WDC has subsequently developed a
       16-bit MPU (W65C816S), an 8-bit microcontroller (with 65C02 as the
       core) named W65C134S, and a 16-bit microcontroller (with 65C816 as
       core).  These are sold off-the-shelf and the the module technology
       is licensed for use in ASIC designs.

       WDC has recently come out with their .8u 134S and 265S.  There are
       many companies who have or are designing in these parts into their
       board-level system design.  It is expected that this new version's
       performance to be greatly enhanced over the previous 1.2u. They
       are also working with their foundry to add EE and Flash versions
       to their standard product offering.

          The Western Design Center
          2166 East Brown Rd.
          Mesa, AZ  85213
          (602)962-4545  Fax: (602)835-6442
          Email: wdesignc@wdesignc.com
          Web: http://www.wdesignc.com

    MC14500 (Motorola)

       According to Magnus Danielson, "This is an awesome chip that
       everyone should know by heart... why?  It's so weird compared to
       most other chips... it is really worth reading up on the details.
       It lives its life inside a 16 pin DIP and has 16 instructions."

       Motorola was the manufacturer of this 1 bit powerhouse, which is
       now out of production.  And no, there isn't a C compiler for it.
       Maybe Dave Dunfield (hi Dave ;-) wouldn't mind adding this to his
       C compiler suite.

       Although the MC14500 is a bit bizarre (one bit's worth) and may be
       somewhat limited, it does have a few noteworthy features:
           - RISC processor with 16 instructions (well, what did you
             expect from a 1 bit processor) and one addressing mode
           - no memory boundary (an infinite amount of memory)
           - small package (16 pin)

       Find a copy of the data sheet on this chip and give it a careful
       going over.  I'm sure you'll agree that this was an interesting
       chip and I imagine was probably quite useful.  Seems to me that
       the new wave of scaled-down micros such as the Atmel 2051,
       MicroChip PIC, and Philips 752 probably caused its demise.

    68HC05 (Motorola)

       The 68HC05 (and the earlier 6805) is based loosely on the
       manufacturer's earlier 6800, with some similarities to the 6502.
       It has a Von-Neuman architecture in which instructions, data, I/O,
       and timers all share the same space.  Stack pointer is 5 bits wide
       which limits the stack to 32 bytes deep.  Some members of this
       family include on chip A/D, PLL frequency synthesizer, serial I/O,
       and software security.

    68hc11 (Motorola and Toshiba)

       The popular 68hc11 is a powerful 8-bit data, 16-bit address
       microcontroller from Motorola (the sole supplier) with an
       instruction set that is similar to the older 68xx parts (6801,
       6805, 6809).  The 68hc11 has a common memory architecture in which
       instructions, data, I/O, and timers all share the same memory

       Depending on the variety, the 68hc11 has built-in EEPROM/OTPROM,
       RAM, digital I/O, timers, A/D converter, PWM generator, pulse
       accumulator, and synchronous and ansynchronous communications
       channels.  Typical current draw is less than 20ma.

    683xx (Motorola)

       The MC68EC300 series incorporates various peripherals into various
       68k family core processors.  These can be called "integrated
       processors".  They are really super-microcontrollers, very high
       performance, capable of high processing speeds, and able to
       address large amounts of memory.  A typical example from this line
       would be the 68331.  It is based on a 68020-like core and has
       about the same processing power as an Intel 80386.

    PIC (MicroChip)

       While watching my 8 year old daughter play with her Barbie Dolls
       (she has about 7 or so, including two that used to belong to Roz,
       my wife, when she was a girl) I noticed an interesting difference
       between the old dolls and the new dolls.  The old Barbies could
       only move their heads sideways, while the new Barbies not only can
       move their heads sideways, but also up and down.  AMAZING - the
       old Barbies were good girls - they could only say no.  The new
       Barbies however can also say yes.  Progress - isn't it wonderful!
       (Not to mention the gymnast Barbie that Dave Perry's daughter got
       for Christmas - "wait'll you see what *she* can do ;-)"

       Which leads me to an amazing fact.  Most everyone thinks of the
       PIC microcontroller line as being a recent introduction.  However,
       they've been popular for over 20 years.  What's the difference?
       Microchip (which was originally [owned by] General Instruments),
       seems to have recreated this microcontroller into a product
       universally regarded as a powerful and cost effective solution.
       The new chips are fabricated in CMOS, some features have been
       added, and new family lines have been introduced.

       The PIC microcontrollers were the first RISC microcontrollers.
       RISC generally implies that simplicity of design allows more
       features to be added at lower cost, and the PIC line is no
       exception.  Although having few instructions (eg. 33 instructions
       for the 16C5X line versus over 90 for the Intel 8048), the PIC
       line has a wealth of features included as part of the chip.
       Separate buses for instructions and data (Harvard architecture)
       allows simultaneous access of program and data, and overlapping of
       some operations for increased processing performance.  The
       benefits of design simplicity are a very small chip, small pin
       count, and very low power consumption.

       PIC microcontrollers are rapidly gaining in popularity.  They are
       being featured more and more often in construction projects in
       popular hobbyist magazines, and are chalking up a good number of
       design wins.  Due to their low cost, small size, and low power
       consumption, these microcontrollers can now be used in areas that
       previously wouldn't have been appropriate (such as logic
       circuits).  They are currently available in three lines:  the
       PIC16C5x, PIC16Cxx, and PIC17Cxx families.

       PSST!  Hey kid!  Want a naked Barbie Doll?!

       Henry Spencer adds the following information:

       The 16C5x line is the descendant of the original PIC design; they
       are a bit limited and clumsy, and have essentially been made
       obsolete by the 16Cxx. The 16Cxx line is the heart of the PIC
       family today, an improved design benefitting from hindsight:
       tidier and more flexible than the 16C5x while retaining its
       simplicity and speed, and providing a wide spread of prices and
       capabilities, including quite a few choices of on-chip
       peripherals.  The 17Cxx line is more ambitious, arguably pushing
       the PIC architecture rather farther than God intended :-) it to
       go; they can do things the 16Cxx line can't, but they're not where
       most of the action is.

       Unusually for microcontrollers, the Microchip PIC databooks
       include complete documentation on how to program the chips --
       information that other manufacturers often will give out only to
       programmer manufacturers, only under nondisclosure, or only at

    COP400 Family (National Semiconductor)

       The COP400 Family is a P2CMOS 4-bit microcontroller which offers
       512 bytes to 2K ROM and 32x4 to 160x4 RAM.  Packages are varied
       from  20 to 28 pin (DIP/SO/PLCC).  Functions include Microwire,
       timers counters, 2.3 to 6.0 Volt operation, ROMless modes, and OTP

       Far from being "old" technology - 4-bit microcontrollers are
       meeting significant market needs in more applications than ever
       before.  The reason for the continuing strength of the COP400
       family is its versatility.  Over 60 different, compatible devices
       are available for a wide range of requirements.  The first under
       $.50 microcontroller set a new standard of value for

    COP800 Family (National Semiconductor)

       The COP800 Basic Family is a fully static 8-bit microcontroller,
       fabricated using double metal silicon gate microCMOS technology.
       This low cost microcontroller contains all system timing,
       interrupt logic, ROM, RAM, and I/O necessary to implement
       dedicated control functions in a variety of applications.

       Depending on the device, features include:  8-bit memory mapped
       architect, MICROWIRE serial I/O, UART, memory mapped I/O, many 16
       bit timer/counters with capture registers, a multi-sourced
       vectored interrupt, comparator, WATCHDOG Timer and Clock monitor,
       Modulator/Timer (high speed PWM timer for IR transmission),
       8-channel A/D converter with prescaler and both differential and
       single-ended modes, brownout protection, halt mode, idle mode,
       high current I/O pins with 15mA sink capability, Schmitt trigger
       inputs and Multi-Input-Wake-Up.  Most devices operate over a
       voltage range from 2.5V to 6V.

       High throughput is achieved with an efficient, powerful
       instruction set operating at a 1uS per instruction rate (most
       instructions are single byte/single cycle) including true bit
       manipulation and BCD arithmetic instructions.  Most devices have
       military versions for -55C to +125C.

    HPC Family (National Semiconductor)

       The HPC Family of High Performance microControllers is a 16-bit
       controller fabricated using National's advanced microCMOS
       technology.  This process combined with an advanced architecture
       provides fast, flexible I/O control, efficient data manipulation,
       and high speed computation.

       With its 16x16 bit multiply and 32x16 bit divide, the HPC is
       appropriate for compute-intensive environments that used to be the
       sole domain of the microprocessor.  The architecture is a
       Von-Neuman architecture where the program and data memory share
       the same address space.

       Depending on the family member, features include: 16-bit
       memory-mapped architecture with software configurable external
       address/data bus, Microwire/Plus serial I/O, UART, 16-bit
       timer/counters with input capture capability, High-Level Data Link
       Control (HDLC) for ISO-standard data communications, 8-channel A/D
       converter with prescaler and both differential and single-ended
       modes, power-saving modes, Multiply/Accumulate Unit with built-in
       circular buffer management for low to medium DSP applications,
       software configurable chip-select outputs, 64KB address space
       directly addressable, low-voltage (3.3V) operation.

       High throughput is achieved with an efficient, powerful
       instruction set operating at a 50ns per instruction cycle (most
       instructions are single byte/single cycle) including true bit
       manipulation.  Key applications currently using the HPC family
       include: Anti-lock Braking Systems, Hard Disk drives for mass
       storage, telecommunications, security systems, laser printers, and
       some military applications.

    Project Piranha (National Semiconductor)

       Project Piranha is an internal code name for National
       Semiconductor's embedded RISC processor technology. The Piranha
       technology represents the first RISC processor specifically
       designed for the needs of embedded applications.  This was
       accomplished through examination of the needs of typical embedded
       applications, resulting in a technology which maintains the
       benefits of CISC while providing the performance of RISC.

       Specifically, some of these benefits are:
         compact code density     -->  smaller memory usage/
                                          lower system cost
         small core size          -->  more room for add-on system design
         scalable architecture    -->  a range of performance solutions
       from 8 to 64 bits             with a common architecture
         common instruction set   -->  you only face the learning curve
            and development tools         once
         modular design           -->  designed for easy integration of
                                          specialized functions into
                                          single chip

       This technology is initially being implemented in application
       specific products from National Semiconductor, with the first
       product being available in Q1, 1995.  For further information on
       this technology, please contact Mark Throndson at
       tmetsc@esd.nsc.com, or (408) 721-4957.

    Z8 (Zilog)

       A "loose" derivative of the Zilog Z80, the Z8 is actually a
       composite of several different achitectures.  Not really
       compatible with the Z80 peripherals.  Has a unique architecture
       with three memory spaces:  program memory, data memory, and a CPU
       register file.  On-chip features include UART, timers, DMA, up to
       40 I/O lines.  Some versions include a synchronous/asynchronous
       serial channel.  Features fast interrupt response with 37
       interrupt sources.  The Z8671 has Tiny Basic in ROM.  The Super-8
       is just that, a super version of the Z8 with more of everything.

       There seem to be quite a few new members of the zilog Z8 family
       arriving recently, including chips such as the Z86C95 which
       contains a fairly "normal" Z8 but with lots of registers (not the
       normal 128, but 236), and an internal 16 bit harvard architecture
       DSP with two data memory systems and one program memory system,
       and with a 24 bit accumulator.  The DSP unit has its memory
       systems accessible as additional banks of Z8 registers (the exact
       mechanism is very poorly explained in the documentation!) so the
       Z8 can be used to write the data and code for the DSP into the
       DSP's storage and then start the DSP running, etc.  There are the
       usual Z8 peripherals plus A/D and D/A (single channel, accessible
       by the Z8 and DSP CPUs).

       Zilog has also recently come out with some new OTP parts:
       part#    PDIP   EPROM      RAM       I/O     type         freq
       Z86E04  18 pin   1K     124 bytes  14 pins  xtal,LC,      8MHz
                                                   cer res,ext
       Z86E08  18 pin   2K     124 bytes  14 pins  xtal,LC,      12MHz
                                                   cer res,ext
       Z86E30  28 pin   4K     237 bytes  24 pins  xtal,LC,RC,   12MHz
                                                   cer res,ext
       Z86E31  28 pin   2K     124 bytes  24 pins  xtal,LC,RC,   8MHz
                                                   cer res,ext

       All parts come with real configurable RAM stack and interrupt
       systems, two fully programmable timers with interrupts, ROM
       protect, low-EMI modes, two analog comparator inputs with
       interrupt capability, low-power standby modes (as low as 1 uA) and
       45 easy instruction set.  There are no separate chip versions to
       do each of the oscillator types, one chip does them all.

    HD64180 (Hitachi)

       A powerful microcontroller with full Z80 functionality plus:
       extended memory management, two DMA channels, synchronous and
       asynchronous communications channels, timers, and interrupt
       controller.  Some versions of this chip also include EPROM, RAM,
       and PIO (programmable input/output).  It runs Z80 code in fewer
       clock cycles than the Z80 and adds in hardware multiply and a few
       other instructions.  Available in versions that run up to 18MHz.

    TMS370 (Texas Instruments)

       It is similar to the 8051 in having 256 registers,  A and B
       accumulators, stack in the register page, etc.  It also has a
       host of onboard support devices, some members have all of them
       while others have a subset, the peripherals include:  RAM, ROM
       (mask, OTP, or EEPROM), 2 timers (configurable as timers/
       counters/comparators/PWM output), watchdog timer, SCI (syncronous
       serial port), SPI (asynchronous serial port), A/D (8 bit, 8
       channel), interrupts.

       Instruction set is mostly 8 bit with some 16 bit support.  Has
       several addressing modes, 8x8 multiply, 16/8 divide.  Clock speeds
       are up to 20MHz which gives 5MHz for buss access and instruction
       cycles.  Pins mostly TTL compatible (except clock and reset).

       Packages include:
             28,40 DIP
             28 CLCC
             28,44,68 PLCC
             40,64 SDIP

       A developers/proto board is available.  It is a multi layer PCB
       about 12"x7" with RS-232 serial I/O, and monitor as well as access
       to all processor pins on a patch and proto area.  Support software
       includes IBM-PC monitor & loader, cross assembler (absolute only).
       A pure serial TTY monitor is also supported.  Sole power
       requirement is +5v.  Priced is about $500 or so.

       A relocating assembler and linker, and a C compiler are also

    1802 (RCA)

       This is a real old-timer.  The 1802 is the successor to the 1801
       (2 chip set) which was the first microprocessor implemented in
       CMOS.  Both products were called microprocessors by RCA, not
       microcontrollers.  However, since the 1801 was implemented in CMOS
       and therefore had low power requirements, it was often used in
       microcontroller applications.  The 1802, with its higher level of
       integration and ease of use, could actually be considered a true
       microcontroller.  The 1802 is radiation hard and used in a lot of
       deep space and satellite applications.

       The 1802 has a fairly clean instruction set, a bunch of
       general-purpose registers (more like a Z80 than an 8051 in that
       regard), and separate data and I/O address spaces.

    MuP21 (Forth chip)

       The MuP21 was designed by Chuck Moore, the inventor of Forth.
       With the MuP21, Forth can compile into machine code and still be
       Forth, because the machine code IS Forth.  The MuP21 freaks out at
       100 MIPS while consuming only 50 milliwatts.  Not only that, the
       chip includes a video generator, has only about 7000 transistors
       (that's right, 7000 and not 7,000,000), and costs about $20.

       The assembler on this chip is a sort of dialect of Forth, as the
       CPU is modeled after the Forth virtual machine.  MuP21 is a
       MINIMAL Forth engine.  In fact MuP21 was designed to run OKAD
       (Chuck Moore's VLSI CAD softare), and OKAD was designed to run on
       MuP21.  OKAD was run on a 486 to design MuP21, and MuP21 was
       designed to have just enough hardware to run OKAD about ten times
       as fast as a 486 on a very cheap chip (the MuP21).  That's the
       reason for the MuP21's on-chip video generator coprocessor.  The
       CPU programs the video generator and then just manipulates the
       video buffer.  It is composite video out, so it only needs one
       pin.  MuP21 is only a 40 pin chip.

       MuP21 chips, boards, software, manuals, and spec sheets are
       available from:
          Offete Enterprises
          1306 South B Street, San Mateo CA 94402
          (415) 574-8250
          Email:  tingch@ccmail.apldbio.com

    F21 (Next generation Forth chip)

       F21 will be bigger (10k vs 7k transistors for the MuP21!) but
       since it is going to implemented with a smaller geometry (.8
       micron vs 1.2) it will still be extremely small and low power, and
       low cost.  Although the specs on this chip aren't final yet,
       expected performance is in the range of 250 MIPS!!.  It will have
       multiple analog processors and a very high speed serial network
       coprocessor on chip.  F21 will also support a wider range of
       memory chips and have more I/O processors.

       Designed for cheap consumer multimedia and parallel processing,
       the F21 is planned for release some time in 1995.

       For more information on this project, contact: Jeff Fox


    In order to get started with microcontrollers, several factors need
    to be considered.
          - cost
          - convenience
          - availability of development tools
          - intended use

    The hardware described in this section is readily available,
    affordable, and is easy to find software for.


6.1)  Evaluation Kits/Boards

    Many manufacturers offer assembled evaluation kits or boards which
    usually allow you to use a PC as a host development system.  Among
    some of the more popular evaluations kits/boards are:

    Parallax Basic Stamp

       This is a small single-board controller that runs BASIC, and costs
       only $39.  A SIP version for only $29 is also available.  THE 256
       byte EEPROM can hold a program of up to about 100 instructions.
       The BASIC Stamp Programming Package is a complete development
       package for only $99.
          Parallax, Inc., 3805 Atherton Rd. 102, Rocklin, CA  95765
          (916)624-8333    Fax: (916)624-8003   BBS: (916)624-7101
          email: info@parallaxinc.com

    Motorola EVBU, EVB, EVM, EVS

       A series of very popular evaluation/development systems based on
       the 68hc11.  Comes complete with the BUFFALO monitor and varying
       types of development software.  Commonly used for university

    Motorola 68705 starter kit

       Motorola supplies a complete development system, -- software,
       hardware, simulator, emulator, manuals, etc for just $100.

    Dallas Semiconductor DS5000TK

       The DS5000TK allows evaluation of any DS5000 series device in any
       existing application without circuit changes.  The included
       DS5000T plugs into the supplied serial interface pod which
       provides a connection to a host PC.  A target cable connects the
       pod to the target system.  Programs can be downloaded directly to
       the chip (no EPROM programming!) using the built-in serial loader.
       (With Dunfield's Development System, you end up with a cheap
       "pseudo-ice".  Dunfield also has a circuit if you want to build a
       similar device.)

    Philips/CEIBO DS750
       For $100 (from Philips, from CEIBO the price is $250), you get a
       "pseudo-ice" for testing your code in-circuit.  Based on the
       low-end Philips 87c75x parts.  Allows source-code debugging in
       assembler (included), C, and PL/M, with an interface similar to
       that of Borland's Turbo Debugger.  Very popular with students and
       consultants for experimenting with 80c51 code.  Includes a VERY
       NICE book which describes the theory of operation of the board
       itself, and includes a good number of experiments that you can try
       for yourself.  Philips sold nearly 10,000 of these boards in the
       USA (and 5000 in Europe without even advertising).

    American Educational Systems AES-51, AES-11, AES-88

       If you'd like to start learning about microcontrollers, but the
       thought of finding all the parts and then building one scares you,
       take a look at the line of boards available from American
       Educational Systems. This might be the easiest way to get started.
       For less than $300, you get a complete and professionally designed
       and packaged educational tool.

       AES has three boards: AES-51 (8051), AES-11 (68hc11), and AES-88
       (8088). All three boards are built along the same lines and
       include RAM, ROM, LCD display, keypad, A/D, serial ports, digital
       I/O ports, and logic probe. Also included is a full bookshelf of
       documentation. These boards are ridiculously easy to use and
       program - you can get started experimenting and designing right

       This is a perfect system for students and hobbyists. Even
       professionals will find this system useful as a prototyping tool
       and test bed. Highly recommended.

       For more information, contact:
             American Educational Systems
             970 West 17th St.
             Santa Ana, CA  92706  USA
             (800)730-3232 or (714)550-8094   Fax: (714)550-9941

6.2)  Easy chips to use

    In addition, several chips provide a similar capability if you are
    willing to spend a bit of time wiring up a simple circuit.  A few
    chips worth looking at are:

    Motorola MC68HC11A8P1
       Contains Motorola's BUFFALO monitor which has the same
       functionality as the one on Motorola's evaluation boards.  A
       working system can be built with this chip and a Maxim MAX-232.
       You can talk to it with a PC or Mac over a 3-wire RS232
       connection.  It is easy to load and run anything you want in the
       on-board RAM and EEPROM.  You can even use subprograms in the
       BUFFALO monitor after getting a listing from Motorola's BBS or ftp
       site.  This BBS/ftp site also has freeware assemblers to make a
       complete development environment cheaply and quickly.

    Intel 8052AH-BASIC
       This popular chip with hobbyists is another easy way to get
       started.  You can download high level code from your host.  The
       disadvantages are that you can't get away from a multi-chip
       solution, the code is noticeably slow, you have to buy an MCS
       BASIC manual, you are detached from the inner workings, there
       aren't many on-chip goodies like A/D, and you can forget about
       running off of a battery.

    Dallas Semiconductor DS5000/DS2250
       These are well suited even for electronics ignoramuses (ignorami?)
       such as myself.  All you need to add is a crystal and two
       capacitors to end up with a working system.  These chips come
       complete with non-volatile RAM in the form of static RAM (at least
       8K) backed up with a lithium battery.  Everything is saved -
       program, data, and bugs ;-).

    MicroChip PIC '5x series
       With only 33 instructions, this chip is definitely easy to use!
       Using Parallax's assembler, the instruction set is ** MUCH ** less
       intimidating than MicroChip's opcodes!  These chips simply need
       power, ground, and 1 of 4 different timing circuits. Doesn't get
       much easier than that!  With I/O pins that are beefy (25mA per pin
       sink, 20mA per pin source) and drive both high and low,
       interfacing is super easy.  It's great to hook LEDs and such
       directly to output pins with only a resister in-line!

6.3)  Software (Cheap and easy)

    Well, it's finally here. A free C compiler for the 8051. Featured in
    Dr. Dobb's August 1997 issue, Andy Yuen's Retargetable Concurrent
    Small C (RCSC) is based on James E. Hendrix' lengendary Small C. A
    previous iteration of RCSC, Concurrent Small C was introduced in the
    August 1996 issue of Dr. Dobbs. With the release of this compiler,
    Andy Yuen is very likely to become a folk hero.

    So, why are you still reading this? The FAQ will wait! First download
    a copy of RCSC. You can get it from: http://www.ddj.com or
    ftp://ftp.mv.com/pub/ddj. Then go out and find a copy of Dr. Dobb's
    August 1997 issue.

    You'll still need to purchase either James E. Hendrix's "A Small C
    Compiler" (ISBN 0-13-814724-8) or the Dr. Dobb's Small C Compiler
    Resource CD. This of course means that the free C compiler isn't
    totally free, but then again, what is?

    A couple free versions of C exist for the 68hc11. One is based on
    Small C and another on the Gnu C package. Neither package is known
    for ease of use or reliability. However, you might find that one of
    these packages fits your needs.

    You can search for free software for development, but you often get
    what you pay for.  What is sorely lacking in freeware is technical
    support.  Several packages are available that provide complete
    development environments for some of the more popular
    microcontrollers.  If you want to be productive right away, think
    about investing $100 or so - it'll be well worth the price!

    I've been playing with the Dunfield Development System lately (on the
    8051), and it's really quite nice.  I've also heard many good things
    about it from others.  It includes a near ANSI-C compiler, run-time
    library with source, assembler, ROM debugger, integrated development
    environment, monitor with source, utilities, and other extras.
    Although not freeware, the low price ($100), the features, all of the
    extra goodies, and the good reviews make this a package worth looking
    at.  Also, if you're interested in working on more than one family of
    microcontroller, Dunfield supports a wide range.  This means only
    needing to learn one system, instead of many.  The following chips
    are supported:  6805, 6809, 68hc11, 68hc16, 8051/52, 8080/85, 8086,
    and 8096.  A package including a simulator and a resident monitor
    debugger are also available for the 8051 for $50.
          Dunfield Development Systems
          P.O. Box 31044, Nepean, Ontario  K2B 8S8   Canada
          (613)256-5820   Fax: (613)256-5821
          Email:  ddunfield@bix.com

    A decent C compiler for the 68hc11 comes from ImageCraft.  This
    package, which runs under DOS and OS/2, includes a near ANSI C
    compiler, assembler, linker, librarian, ANSI C functions and headers,
    and 90 page manual.  The current release is version 1.02 of their
    compiler.  The price is just $40.  Initial feedback on this compiler
    seems promising.  The pre-release versions are already in use by many
    of you, and will still be available as freeware.
          P.O. Box 64226, Sunnyvale, CA 94086-9991
          (Richard Man) imagecft@netcom.com

    Another low priced ($100) C compiler comes from Micro Computer
    Control.  Cross compilers running under DOS are available for the
    8051 and the Z8 (including Super-8).  This package includes a C
    compiler, assembler, linker, librarian, and extensive printed
    documentation.  A simulator/source code debugger is available for an
    additional $79.95.
          Micro Computer Control Corporation
          PO Box 275, 17 Model Ave., Hopewell, NJ  08525
          (609)466-1751   Fax: (609)466-4116   BBS: (609)466-4117
          Email: 73062.3336@compuserve.com

    C isn't the only development system available (yeah, I know that's
    hard to believe) - good solid Basic and Forth development systems are
    also available.  Refer to the appropriate FAQ for the microcontroller
    that you are using for more information on free and commercial
    development systems.

    If the Microchip PIC is your game, then check out the Parallax tools
    (available on their ftp and web sites).  All Parallax software is
    available free of charge to all takers!  This includes PSIM (a PIC
    simulator), PASM (an assembler for '5x parts), and PASMX (an
    assembler for 'xx parts).  These are the full commercial versions,
    not hobbled in any way!


    Just a bit of an introduction for the beginner.

7.1)  Machine/Assembly language

    Machine language is the program representation as the microcontroller
    understands it.  It is not easy for humans to read and is a common
    cause of migraine headaches.  Assembly language is a human-readable
    form of machine language which makes it much easier for us flesh and
    bone types to deal with.  Each assembly language statement
    corresponds to one machine language statement (not counting macros).

    An assembly/machine language program is fast and small.  This is
    because you are in complete charge of what goes into the program.  Of
    course, if you write a slow, large, stupid program, then it will run
    slowly, be too big, and be stupid.  Assembly language (assembler)
    can't correct stupidity - although sometimes I wish it could ;-).

    If you are starting out learning about microcontrollers, it would be
    worth your while first learning assembler.  By programming in
    assembler, you master the underlying architecture of the chip, which
    is important if you intend to do anything significant with your

7.2)  Interpreters

    An interpreter is a high level language translator that is closer to
    natural language.  The interpreter itself is a program that sits
    resident in the microcontroller.  It executes a program by reading
    each language statement one at a time and then doing what the
    statement says to do.  The two most popular interpreters for
    microcontrollers are BASIC and FORTH.

    BASIC's popularity is due to its simplicity, readability, and of
    course just about everyone has at least played with BASIC at one time
    or another.  One common compaint about [interpreted] BASIC is that it
    is slow.  Often this can be solved by using a different technique for
    performing the desired task.  Other times it is just the price paid
    for using an interpreter.

    FORTH has a very loyal following due to its speed (approaching that
    of assembler language) and its incremental approach to building a
    system from reusable parts.  Many FORTH systems come with a host
    system which turns your desktop computer into a development system.
    FORTH can be quite difficult to write in (if you have no experience
    with it) and is probably even harder to read.  However, it is a very
    useful and productive language for control systems and robotics, and
    can be mastered in time.

    JVM - Java(TM) Virtual Machine - was added lately to the list of
    interpreters, after the invention of the language and concepts by Sun
    Microsystems. Java was adopted enthusiastically by programmers all
    over the world and has finally found its way into the embedded
    environment. Java provides a new and revolutionary concept, geared
    towards the use of portable software applications which can be
    dynamically downloaded over a network, rather than kept on the local
    disk or in the local memory of a specific computer.  This way, the
    client computer does not need to keep all the applications, since
    they can be dynamically downloaded from the server whenever required.
    Another Java main feature is its Operating-System independent
    capability. Java is also a language. The Java language is a new
    object-oriented programming language, also developed by Sun
    Microsystems. In its very own architecture it is particularly suited
    to the development of Java's portable application pieces of software,
    called applets.

    The nicest thing about developing a system with an interpreter is
    that you can build your program interactively.  You first write a
    small piece of code and then you can try it out immediately to see
    how it works.  When the results are satisfactory, you can then add
    additional components until the final product is achieved.

7.3)  Compilers

    A compiler is a high level language translator that combines the
    programming ease of an interpreter with greater speed.  This is
    accomplished by translating the program (on a host machine such as a
    desktop PC) directly into machine language.  The machine language
    program is then burned onto an EPROM or downloaded directly to the
    microcontroller.  The microcontroller then executes the translated
    program directly, without having to interpret first.

    The most popular microcontroller compilers are C and BASIC.  PL/M,
    from Intel, also has some popular support due to that company's
    extensive use of that language. Modula-2 has a loyal following due to
    its efficient code and high development productivity. Ada has many
    adherents among those designing on the larger chips (16 bits and

    Due to both its popularity and its slow speed, it was only logical
    that BASIC would appear as a compiled language.  A few companies
    supply a BASIC compiler for several of the more popular
    microcontrollers.  Execution speed is drastically increased over
    interpreted BASIC since the microcontroller is freed from the task of
    interpreting the statements as the program runs.

    While interpreted Forth approaches (and sometimes surpasses) the
    speed of many compilers, compiled Forth screams along.  Today there
    are many high performance optimizing native code Forth compilers, and
    there are also lots of very cheap or free public domain Forths.  Some
    of them like Tom Almy's ForthCMP produces optimized native code with
    less overhead and better performance than just about anything else
    out there.  Of course it still has compactness and more elegant
    factoring of functionality than in most languages.

    C is now the language of choice for the entire universe.  C is used
    on computers from the tiny microcontroller up to the largest Cray
    supercomputer.  Although a C program can be a bit tedious at times to
    read (due to the terse programming style followed by many C
    programmers), it is a powerful and flexible development tool.
    Although a high level language, it also gives the developer access to
    the underlying machine.  There are several very good and cheap C
    compilers available for the more popular microcontrollers.  It is
    widely used, available, supported, and produces fairly efficient code
    (fast and compact).

7.4)  Fuzzy Logic and Neural Networks

    Fuzzy Logic and neural networks are two design methods that are
    coming into favor in embedded systems.  The two methods are very
    different from each other, from conception to implementation.
    However, the advantages and disadvantages of the two can complement
    each other.

    The advantage of neural networks is that it is possible to design
    them without completely understanding the underlying logical rules by
    which they operate.  The neural network designer applies a set of
    inputs to the network and "trains" it to produce the required output.
    The inputs must represent the behavior of the system that is being
    programmed, and the outputs should match the desired result within
    some margin of error.  If the network's output does not agree with
    the desired result, the structure of the neural network is altered
    until it does.  After training it is assumed that the network will
    also produce the desired output, or something close to it, when it is
    presented with new and unknown data.

    In contrast, a fuzzy-logic system can be precisely described.  Before
    a fuzzy control system is designed, its desired logical operation
    must be analyzed and translated into fuzzy-logic rules.  This is the
    step where neural networks technology can be helpful to the
    fuzzy-logic designer.  The designer can first train a software neural
    network to produce the desired output from a given set of inputs and
    outputs and then use a software tool to extract the underlying rules
    from the neural network.  The extracted rules are translated into
    fuzzy-logic rules.

    Fuzzy logic is not a complete design solution.  It supplements rather
    than replaces traditional event control and PID (proportional,
    integral, and derivate) control techniques.  Fuzzy logic relies on
    grade of membership and artifical intelligence techniques.  It works
    best when it is applied to non-linear systems with many inputs that
    cannot be easily expressed in either mathematical equations used for
    PID control or IF-THEN statements used for event control.

    In an effort to change fuzzy logic from a "buzzword" (as it is in
    most parts of the world) to a well established design method (as it
    is in Japan), most manufacturers of microcontrollers have introduced
    fuzzy logic software.  Most software generates code for specific
    microcontrollers, while other generates C code which can be compiled
    for any microcontroller.


    Having a programming language is usually not enough to develop a
    program for a microcontroller.  Some way of debugging your program is
    needed.  I am only too painfully aware of this fact.

8.1)  Simulators

    A simulator runs your microcontroller program on a host machine (such
    as your PC).  You can step through the code to see exactly what is
    happening as the program runs.  Contents of registers or variables
    can be altered to change the way the program runs.  Eliminates (or at
    least delays) the erase/burn/program EPROM cycle common in
    microcontroller program development.  You can work out ideas or learn
    about microcontrollers by experimenting with small code fragments and
    watching on the screen what happens.  A simulator can't support real
    interrupts or devices, and usually runs much slower than the real
    device the program is intended for.

    Some manufacturers have a cross between a software simulator and the
    hardware emulator - a hardware simulator.  This is a piece of
    equipment that plugs into your target, and the pins will toggle and
    react like they should - just MUCH slower.  Cost of a device like
    this is only about $100.  Two such boards by National Semiconductor
    and Philips are detailed in section 6.2.

8.2)  Resident Debuggers

    A resident debugger runs your program on the microcontroller itself,
    while showing the progress on your host machine (such as a PC).  Has
    many of the same advantages as simulator above, with the additional
    benefit of seeing how the program runs on the real target machine.  A
    resident debugger needs to "steal" some resources from the target
    machine, including: a communications port to communicate with the
    host, an interrupt to handle single stepping, and a certain amount of
    memory for the resident part (on the target) of the debugger.

8.3)  Emulators

    If you've got the money, this is the equipment you want to develop
    your system with (yeah, that's right, a preposition at the end of a
    sentence!).  A [usually] expensive piece of hardware that even for
    the cheaper versions will run you at least $700.  An emulator is a
    sophisticated device that pretends that it is the microprocessor
    itself, while at the same time capturing information.  It provides
    full and total control over your target, while at the same time not
    requiring any resources from the target.  The emulator can either be
    a stand alone device with its own display, or it can be interface to
    a PC.

8.4) Java on Embedded Systems


    This is a short discussion about the technology of Java (TM)
    implementation on Embedded Systems and the issues involved. This
    technology implementation can bring to the embedded systems world the
    benefits of Java, enabling the development of  extensible, portable
    and downloadable applications, which dramatically reduce development
    costs and provide fast response to ever changing market demands,
    while keeping all existing advantages.

    Java -  Write once, run everywhere ...
    Java provides a new and revolutionary concept, developed by Sun
    Microsystems and geared towards the use of portable software
    applications which can be dynamically downloaded over a Network,
    rather than kept on the local disk or in the local memory of a
    specific computer. This way, the client computer does not need to
    keep all the applications, since they can be dynamically downloaded
    from the  server whenever required. After the applications are done,
    they can be either kept on the computer or discarded - as required.
    Of course, these applications do not need to exist when the computer
    is built or purchased - they, or their later versions, can be
    developed and added at a later stage. Java enables dynamic
    interaction, where the user receives immediate feedback. Java
    provides Operating-System independent capability. Java provides all
    these features by allowing the execution of code that can be
    distributed across the network in a portable, robust, secure and
    high-performance environment.

    Java - The Language
    The Java language is a new object-oriented programming language, also
    developed by Sun Microsystems. In it's very own architecture it is
    particularly suited to the development of Java's portable application
    pieces of software, called applets.  These are applications which are
    dynamically downloaded over the network and executed on the
    Java-Enabled client computer, normally equipped for this purpose with
    a Java-Enabled Web Browser.

    Java - The Components
    The Java system compiles Java applets into Byte Code. Once compiled,
    the Java Byte Code is placed in a file ready to be downloaded through
    the Network to the client computer that requests it. A Java-Enabled
    Web Browser includes a component called a Java Virtual Machine (or
    JVM, for short). This component is responsible for actually running
    the Java Byte Code and it isolates the Java code from the specifics
    of the underlying hardware  and operating system. Consequently, Java
    applets are developed once but they can run, unchanged, on any client
    computer with a Java Enabled Web Browser, regardless of the specific

    Implementation of Java in Embedded Systems
    The use of Java in an embedded environment presents unique
    challenges, due to the fundamental differences between an embedded
    system and a general-purpose computer or work-station. These
    differences should be thoroughly understood in order to better
    appreciate the implications associated with implementing Java to a
    particular application domain.
    a. An embedded system usually lacks secondary storage (e.g. a hard
    disk) making it difficult to keep a library of application code and
    to load a particular routine upon demand. Therefore, the size of the
    application is limited to the size of the existing memory device
    (such as ROM or Flash).
    b. In most cases, an embedded system lacks direct user interface such
    as a monitor. Rather, it communicates with the operator (if at all)
    through some specialized devices or through a front-end station which
    is connected to the embedded application  via a specialized bus or
    c. The lack of a file-system and traditional user interface devices
    has a special significance for Java-based applications which rely
    heavily on the presence of these components. Often, an embedded
    application has limited resources such as memory and CPU bandwidth.
    Consequently, the scheduling  and sharing of these resources become
    one of the major design challenges when developing such an
    application. Particularly, in Real-Time applications, the performance
    requirements and the constraints on resources lead to lean and
    fine-tuned scheduling disciplines in order to meet the system's
    performance requirements.
    d. Typically, an embedded system is very specialized; it is tightly
    integrated with the surrounding environment and has demanding
    requirements for robustness. Since the protection mechanisms (such as
    address-space boundary protection) that are usually provided by a
    typical operating system are not available in such an environment,
    the mechanism of introducing new software into the application should
    be tightly controlled. This fact has special significance in the
    context of Java where the programming paradigm is based on dynamic
    downloading of applets from various sources. Java was designed (and
    initially implemented) to run on UNIX workstations. It relies on many
    services that are available on such a system (such as files,
    processes, Internet naming services) which do not exist in a typical
    embedded system. Some of these do not make sense in such an
    environment (for example, a network device might have an IP-address,
    but it does not necessarily have a domain name).

    Implementation Architectures
    In order to execute Java code on an embedded system, several key
    components must be developed or ported to this system. These
    components have to be tailored to the specific hardware, to the
    kernel (if one exists) and to some extent to the C compiler being
    used (since part of the JVM and its interface layers are implemented
    in C). The two main possible approaches are:
    a. Developing a dedicated Java-compatible system, exactly fitted to
    the embedded environment.
    b. Porting Sun's original Java to the embedded environment.
    The first approach has the advantage of ending with a product which
    is originally designed to the embedded environment, including all the
    constraints of this special environment. The second approach has the
    advantage of compatibility to the de-facto standard which has been
    already adopted by the industry. Since Java is a live language and
    environment, driven by both the industry needs and the rapid
    technology changes, this factor is considered to be of tremendous

    More architectural concepts
    For achieving appropriate compatibility with all Java existing and
    future intrinsics, the only possible approach of porting Java is
    based on Sun's JDK (Java Development Kit) sources as distributed from
    Sun. These sources were analyzed and checked against the requirements
    of the embedded environment, before being carefully restructured.
    The final result is retargetable software which lends itself to be
    easily ported to each unique combination of hardware - kernel - C
    compiler. This software runs on a variety of Real-Time Operating
    Systems and provides a Virtual Machine environment for the execution
    of Java byte code. Special design considerations enable it to coexist
    with other applications, which are running on the same platform,
    either Real-Time or Non-Real Time, while complying with the
    constraints imposed by the Real-Time  Operating System and the
    application tasking architecture.

    JVM Encapsulation
    As mentioned previously, the ideal technique would be the one which
    enables the embedded Java software to run on top of any commercial
    Real-Time kernel or be adapted to any application-specific executive.
    This capability is accomplished by having a well-defined API that
    encapsulates the services that the JVM needs from the underlying
    system.  The Java language supports parallelism in the form of
    threads (light-weight tasking). It includes methods for thread
    management, synchronization and communication. There are two
    approaches for mapping the Java threads to the parallel  entities of
    the underlying kernel (typically, they are called tasks):
    a. Mapping each Java thread to a kernel task and utilizing the kernel
    services to schedule these threads and synchronize between them.
    b. Dedicating one kernel task to run the JVM and then have the Java
    threads be implemented internally by the Java run-time support
    Again, there are tradeoffs to be considered when choosing the
    appropriate model. In the first model, the services of the Real-Time
    kernel are used directly for managing the Java threads and can, in
    some situations, perform better. In addition, Java threads can
    interact directly with other tasks in the system. However, this
    approach requires that the overall system be fully tested each time a
    new Java thread is introduced or a change to the Java code is
    performed. In the second approach, the JVM acts also as an
    intermediate monitor, which internally manages the Java threads and
    ensures  that the Java code as a whole performs accurately within its
    resource boundary. It therefore ensures that in any circumstances
    the JVM does not exceed the amount of system resources allocated to
    the Java application.  The practical meaning of this implementation
    approach is that once the JVM has been fully tested in a particular
    environment,  the different applets can be downloaded and executed
    with no need to re-test.

8.5)  Good Stereo System

    This is the most important tool for the microcontroller developer, or
    for any computer system developer for that matter.  Don't expect to
    get anywhere unless you have the proper music playing in the
    background(?) at the proper volume.  I find that I do my best work
    with the Rolling Stones (especially Goats Head Soup) or Clapton
    (especially early stuff like Cream - Disraeli Gears is a killer
    album!).  The volume must be set to cause excrutiating pain to be
    most effective.  Trust me on this ;-).

    Tom Mornini of Parallax reports:  "Johnny Cash also has a certain
    effectiveness, as well as the Beatles, Aerosmith, and Rush!  60's
    rock and British invasion bands in particular seem to have a
    particularly productive effect."

    This would be an interesting topic for an in-depth study.
    Particularly intriguing, is if certain types of music work better
    with specific [families of] processors.  Another question in need of
    study would be if it's really true that the smaller the chip (in
    bits), the louder the music needs to be.


    If you are interested in learning more about microcontrollers, there
    are many fine sources of information.  You have your choice of
    printed media (books, periodicals, informative graffiti) or
    interactive (right here on the Internet, or BBSs).

9.1)  Books

    8-bit Microcontroller Instruction Set Performance
        - Digitial Systems Consulting / June 1994
        - compares Motorola's M68HC05, Intel's 80x51,
            Microchip's PIC16C5x, and National's COP8
        - lit number 630008
        - (800)272-9959 call this number for copies

    The 16 bit 8096:  Programming, Interfacing, Applications
        - Ron Katz and Howard Boyet
        - Microprocessor Training Inc
          14 East 8th Street, New York, NY  10003
        - Library of Congress Catalog card number:  85-61954
        - According to William Chernoff:  "The book is pretty good -
          mostly software examples.  The one hardware thing I looked
          closely at was wrong - a schematic error.  Oh well."

    The 68hc11 Microcontroller
        - Joseph D. Greenfield (at R.I.T.)
        - Saunders College Publishing, (Harcourt Brace Jovanovich)
        - 1992
        - ISBN 0-03-051588-2
        - A number of the sections make use of the Buffalo monitor.
          This could be useful if you are using the Motorola Trainer EVB.

    The 8051 Family of Microcontrollers
        -Richard H. Barnett
        -Prentice-Hall, 1995 (yeah, that's right, 1995!)
        -ISBN 0-02-306281-9

    8051 Interfacing and Applications
        - Applied Logic Engineering
          13008 93rd Place North, Maple Grove, MN  55369
        - (612)494-3704

    The 8051 Microcontroller
        - I. Scott MacKenzie
        - Prentice Hall
        - 2nd edition, 1995
        - ISBN 0-02-373660-7
        - includes schematics for a single-board computer,
          assembly-language source code for a monitor program, and
          interfaces to a keypad, LEDs, and loudspeaker

    The 8051 Microcontroller
        - James W. Stewart
        - Regents/Prentice-Hall, 1993
        - $27.50, 273 pages
        - includes many interfacing examples (switches, solenoids,
          relays, shaft encoders, displays, motors, and A/D converters)
          and a chapter on top-down design method

    The 8051 Microcontroller: Architecture, Programming and Applications
        - Kenneth J. Ayala
        - 241 pages, soft cover
        - 5.25" diskette with assembler and simulator
        - ISBN 0-314-77278-2, Dewey 004.165-dc20
        - West Publishing Company
          P.O. Box 64526, St. Paul, MN  55164
        - see review in next section

    The Art of Programming Embedded Systems
        - Jack G. Ganssle
        - 1992, 279pp, $55.00
        - ISBN: 0-12-274880-0
        - CONTENTS: Introduction, Initial Considerations.  Elegant
          Structures.  Designs for Debugging.  Design for Test.  Memory
          Management.  Approximations. Interrupt Mamangement.  Real-Time
          Operating Systems.  Signal Sampling and Smoothing.  A Final
          Perspective.  Appendixes: Magazines, File Format.  Serial
          Communications.  Bibliography.  Index.

    Assembly Language Programming (for the MCS-51 family)
        - F. A. Lyn
        - L. S. Electronic Systems Design

    Basic-52 Programmer's Guide
        - Systronix, Inc. (they also sell a Basic compiler)
        - address above

    Beginner's Guide
        - Suncoast Technologies

    A Beginners Guide to the Microchip PIC
        - Nigel Gardner
        - Character Press, Ltd. (UK)
        - ISBN 1 899013 00 8
        - software (on floppy) and hardware guide, debugging techniques
        - suitably titled, for those with no previous microcontroller
        - 19.95 UK Pounds

    The PIC Source Book:
        - assembly language source code on diskette
        - $39
        - Scott Edwards Electronics
          964 Cactus Wren Lane, Sierra Vista, AZ  85635
          (602)459-4802    Fax: (602)459-0623

    C and the 8051
        - Thomas W. Schultz
        - Prentice Hall
        - ISBN 0-13-753815-4

    Data Acquisition and Process Control with the M68HC11 Microcontroller
        - Frederick Driscoll, Robert Coughlin, Robert Villanucci of
          Wentworth Institute of Technology.
        - Macmillan Publishing Company
        - 1994
        - ISBN 0-02-33055-X
        - Several Chapters on the 68HC11, instructions, and EVB;
          chapters on interfacing Analog and Digital signals to the
          68HC11;  example applications of interfaces to temperature,
          load cell, pressure and thermocouple sensors.
        - a good companion to Motorola's "pink" books

    Data book / Handbook / Users' Guide
        - Advanced Micro Devices
        - Dallas (User's guide for the DS5000)
        - Intel
        - Siemens

    Design with Microcontrollers
        - John B. Peatman
        - ISBN 0-07-049238-7
        - This book is on a more advanced level.  Uses both the 68hc11
          and Intel 8096 as example systems.
        - Used for a very popular course on microcontroller design at
          Georgia Tech.

    Embedded Controller Forth for the 8051 Family
        - Academic Press
        - William H. Payne
        - uses a Forth development system available on the Internet

    Embedded Controllers Databook 1992 Edition
        - National Semiconductor Corporation
        - literature number: 400049
        - (800)272-9959 call this number for for copies

    Embedded Systems Programming in C and Assembler
        - John Forrest Brown
        - Van Nostrand Reinhold, 1994
        - 304 pages, $49.95
        - ISBN 0-442-01817-7
        - covers Motorola and Intel processors
        - includes diskette with code from the book
        - book review in Dr. Dobb's Journal, November 1994, page 121

    Experimenter's guide
        - Rigel Corporation

    Introduction to Microcontroller Design, Based on the 8051 family of
        - Business Data Computers
          P.O. Box 1549, Chester, CA  96020

    Mc68hc11 An Introduction
        - Han-Way Huang
        - Software and Hardware Interfacing, Applications using the
          EVB from Motorola.
        - West Publishing Company
        - ISBN 0-314-06735-3

    M68hc11 Reference Manual
        - Motorola - literature reference M68HC11RM/AD
        - This document is the "bible" of the 6811 and is a must-have
          for any serious 6811 programmer.

    MC68hc811E2 Programming Reference Guide
        - Motorola - literature reference M68HC811E2RG
        - A pocket-sized guide to the version of the 6811 used on the
          Mini Board

    The Microcontroller Idea Book
        - Jan Axelson (of Microcomputer Journal fame)
        - features the 8052-BASIC microcontroller
        - hands-on guide with complete plans (schematics, design theory,
          program listings, construction details, etc)
        - explains how to use sensors, relays, displays, clock/calendars,
          keypads, wireless links, and more
        - 1994, 273 pages, $31.95 + shipping
        - Lakeview Research, 2209 Winnebago St., Madison, WI  53704
          (608)241-5824  Internet: 71163.3555@compuserve.com
        - contact the author at janaxel@aol.com

    Microcomputer Engineering
        - Gene H. Miller
        - Prentice Hall, Englewood Cliffs, NJ  07632
        - 1993
        - ISBN 0-13-584475-4
        - Explains the basics.  Many clear and concise assembly language
          example programs.
        - Written to be used with the Motorola Trainer (EVB).

    Microcontroller Technology, The 68hc11
        - Peter Spasov
        - Prentice Hall
        - ISBN 0-13-583568-2

    Microcontrollers: Architecture, Implementation, and Programming
        - Kenneth Hintz and Daniel Tabak
        - McGraw-Hill Inc.  1992
        - ISBN 0-07-028977-8

    Microprocessor 1995
        - Jack Quinn, Micrologic Research
        - Integrated Circuit Engineering Corporation
          15022 North 75th St., Scottsdale, AZ  85260-2476
          (602)998-9780   Fax: (602)9481925
        - comprehensive study of the microprocessor industry and market,
          current status, trends, and developments
        - $1495
        - Microprocessor 1996 due out in November

    PIC 16Cxx Development Tools instructions manuals
        - Parallax, Inc.
        - Instruction manual for the Parallax PIC assemblers
        - Instruction manual for the Parallax Software Simulator
        - Instruction manual for the Parallax PIC programmer hardware
        - Details the Parallax PIC instruction set

    PIC 16Cxx Applications Handbook
        - Parallax, Inc.
        - Contains condensed data sheets for '5x, '64, '71, and '84
        - Contains 14 application notes showing circuits and code for
          common projects using the PIC series of microcontrollers.

    Easy PIC'n, A Beginner's Guide to Using PIC16/17 Microcontrollers"
        - ISBN 0-9654l62-0-8
        - intended to ease the beginner toward understanding and
          application of the PIC16/17 line of microcontrollers from
          microchip Technology Inc.  For the hobbyist or engineer for
          self study or as a text for a college engineering course in the
          application of microcontrollers.
        - examples of assembly language programs
        - in-depth coverage of program writing using flow charts
        - the approach is hands-on with lots of examples, all of which
          may be demonstrated using a very simple demo board (a project)
          described in the beginning of the book
        - For more information, contact the author:
                David Benson, Author (Easy PIC'n)
                Owner, Square 1 Electronics
                (707)279-8881   Fax: (707)279-8883

    Posix.4:  Programming for the Real World
        - Bill O. Gallmeister
        - O'Reilly and Associates, 1995
        - ISBN 1-56592-074-0
        - Part I of the book describes the Posix standard (what it is,
          what it isn't, and what it's for), and explains the principles
          of real time programming (tasking, messages, scheduling, I/O,
          and performance) and why Unix isn't fit for real-time
          programming.  Part II is a reference on the Posix functions and
          header files.  Part III contains much of the code for the
          exercises in the book.

    Programmer's Guide to the 1802
        - Tom Swan
        - Hayden Book Company, Inc., 1981
        - ISBN 0-8104-5183-2
        - good introduction to assembly language progamming and an
          thorough tutorial on the 1802

    Programming Microcontrollers in C
        - Ted Van Sickle
        - HighText Publications, 1994
        - 394 pages, $29.95
        - ISBN 1-878707-14-0
        - thorough tutorial on C programming, covers aspects of C
          programming specific to embedded systems
        - covers the Motorola line of microcontrollers (small to large)
        - book review in Dr. Dobb's Journal, November 1994, page 121

    The Real-Time Kernel
        - Jean Labrosse
        - R&D Publications, Inc.
          Suite 200 1601 W 23rd St., Lawrence, KS  66046
        - (913)841-1631   Fax: (913)841-2624
        - Based on the article "A Portable Real Time Kernel in C"
          in Embedded Systems Programming (Part 1: vol 5 no 5
          May 1992, Part 2: vol 5 no 6 June 1992)
        - originally written for the Intel 186 but ported to HC11
          source code for UCOS11

    Single- and Multiple-Chip Microcomputer Interfacing
        - G.J. Lipovski
        - Copyright 1988
        - 478 pages
        - ISBN 0-13-810557-X (Prentice-Hall Edition)
          ISBN 0-13-810573-1 (Motorola Edition)
        - Based around the 68HC11 it covers both hardware and
          software at undergraduate level, but the emphasis is on
        - Chapter titles:
               1  Microcomputer Architecture
               2  Programming Microprocessors
               3  Bus Hardware and Signals
               4  Parallel and Serial I/O
               5  Interrupts and Alternatives
               6  Analog Interfacing
               7  Counters and Timers
               8  Communications Systems
               9  Storage and Display Systems

    Single- and Multiple- Chip Microcomputer Interfacing (Lab Manual)
        - Peter Song and G. Jack Lipovski
        - Prentice-Hall, 1988
        - ISBN 0-13-811605-9
        - Support for the above book.  Examples based around the Motorola
          EVB and the BUFFALO monitor or the EVBU (or 3-chip micro) and

    User Manual for the CDP1802 COSMAC Microprocessor
        - RCA, 1977
        - contains useful hardware and software techniques

    Using the M68HC11 Microcontroller: A Guide to Interfacing and
    Programming, 1/e
        - John C. Skroder, Texas A & M, Institute of Electronics
        - Prentice Hall, 1996, $77.00
        - Copyright 1997, 627 pp. cloth
        - ISBN 0-13-120676-1
        - Table of Contents
               1.  Introduction to the M68HC11.
               2.  M68HC11 Resets and Interrupts.
               3.  M68HC11 Parallel I/O.
               4.  Parallel I/O Using the Simple-Strobed and
                   Full-Handshake Modes.
               5.  The M68HC11 Serial Communications Interface (SCI).
               6.  The M68HC11 Serial Peripheral Interface (SPI).
               7.  M68HC11 Free-Running Counter and Input Captures.
               8.  M68HC11 Output Compare Functions.
               9.  M68HC11 Forced Output Compares, Real-Time Interrupts
                   and Pulse Accumulator.
               10. M68HC11 Analog-to-Digital Conversions and Fuzzy
               11. M68HC11 Expanded-Multiplexed Mode.
               Appendix A. M68HC11EVB Board.
               Appendix B. M68HC11EVBU Board.
               Appendix C. Connecting the EVB/EVBU to External Circuits.
               Appendix D. AS11 Assembler.
               Appendix E. M68HC11 Instruction Set.
               Appendix F. Parts/Equipment Listing.

9.2)  Data and Reference Books

        - M68hc11 Reference Manual, ref # M68HC11RM/AD
             this document is the "bible" of the 6811 and is a must-have
               for any serious 6811 programmer
             contact Motorola at 800-521-6274 (in the U.S.) to get a free
               copy of this manual
        - MC68hc811E2 Programming Reference Guide, ref # M68HC811E2RG
             a pocket-sized guide to the version of the 6811 used on the
             Mini Board, "ownership of this handy reference is proof of
             being a true 6811 nerd" - by Fred Martin

    National Semiconductor - (800)272-9959 for copies
        - COP8 Databook, ref # 400007
        - COP8 Selection Guide, ref # 630006
        - COP8 Designers Information Kit, ref # 6300007-005
             contains: - COP8 Databook (1994 Edition)
                       - COP8 Selection Guide (1994 Edition)
                       - Independent 8-bit Instruction Set Analysis
                       - Independently prepared software analysis of
                         National's COP8, Motorola's M68Hc05, Intel's
                         80X51, and Microchip's PIC16C5X
                       - Utility and Overview Disks
                       - Self-lead overview on COP8, includes electronic
                         selection guide and sample application code
        - COP8 Utility Disk, Mac ref # 6300000, Windows ref # 630001
             typical microcontroller applications and sample code
             available by ftp nscmicro.national.com in/pub/COP8
        - COP8 Overview Disk, Mac ref # 630004, Windows ref # 630005
             self-lead COP8 overview, shows product features/benifits
                and includes a electronic selection guide (2 disks)
             available by ftp nscmicro.national.com in /pub/COP8

9.3)  Periodicals

    Various magazines and journals (journals seems to be THE popular name
    for magazines these days) provide articles from time to time on
    microcontrollers.  If you are just starting out learning, pick those
    magazines that feature construction articles.

    The Computer Applications Journal (Circuit Cellar Ink)
        - programming and construction articles
        - POB 7694, Riverton, NJ  08077-8784
        - Fax: (203)872-2204
        - Voice orders: (609) 786-0409
        - On-line orders (BBS): (203) 871-1988
        - Email orders: ken.davidson@circellar.com
        - $21.95, $31.95 surface Canada and Mexico,
          $49.95 air all other countries

    Computer Design
        - industry announcements and trends
        - One Technology Park Drive, P.O. Box 990, Westford, MA  01886
        - (508)692-0700

    The Computer Journal
        - programming and construction articles, specializing in old
          computers (S-100, CP/M, TRS-80, Xerox, Adam, etc)
        - P.O. Box 3900, Citrus Heights, CA 95611-3900
        - (800)424-8825 or (916) 722-4970   FAX: (916) 722-7480
        - BBS: (916) 722-5799
        - WWW: http://www.psyber.com/~tcj
        - Email: tcj@psyber.com
                 Dave Baldwin: dibald@netcom.com
                 Bill Kibler: kibler@psyber.com
        - USENET newsgroup alt.tcj

    Control Engineering
        - industry outlook on control, instrumentation, and automation
        - Cahners Publishing
        - Circulation:
          8773 S. Ridgeway Blvd., Highlands Ranch, CO  80126-2329
        - Editorial/Executive Offices:
          1350 E. Touhy Ave, P.O. Box 5080, Des Plaines, IL 60017-5080

    Dr. Dobbs Journal
        - programming articles, concepts, and designs
        - 411 Borel Ave., San Mateo, CA  94402
        - (415)358-9500

        - Cahners Publishing Company
          8773 South Ridgeline Blvd., Highlands Ranch, CO 80126-2329
        - annual microprocessor and DSP editions
        - http://www.ednmag.com/

    Electronic Engineering Times
        - industry announcements and trends
        - 500-B Bi-County Boulevard, Farmingdale, NY  11735
        - (516)293-3000

    Electronics Now
        - construction articles
        - Box 55115, Boulder, CO  80321-5115
        - $19.97 one year

    Elektor Electronics
        - programming and construction articles
        - World Wide Subscription Service Ltd
          Unit 4, Gibbs Reed Farm, Pashley Road
          Ticehurst TN5 7HE, England
        - 27 UK pounds
        - Old Colony Sound Lab, P.O. Box 243, Peterborough, NH 03458
        - Tel. (603) 924-6371, 924-6526
        - Fax: (603) 924-9467
        - $57 USA and Canada per year

    Embedded Systems Programming
        - programming and systems design articles
        - Miller Freeman Publications
        - 500 Howard St., San Francisco, CA  94105
        - Miller Freeman: (415)905-2200
          Embedded Systems Programming phone: (800)829-5537

    Forth Dimensions
        - monthly magazine on Forth
        - Forth Interest Group, P.O. Box 2154, Oakland, California 94621
        - (510)893-6784   Fax: (510)535-1295
        - Email: johnhall@aol.com
        - Forth Interest Group home page:

    Inquisitor Magazine
        - If you're the type that watched Gilligan's Island for its
          socio-political insights, then you'll love a new 'zine that
          just crossed my desk - Inquisitor Magazine.  It's general
          philosophy seems to be ... well, it seems to be ... uh, yeah!
          Technical in nature, bizarre, tongue in cheek, eclectic,
          electric, did I mention bizarre(?), and lots of fun.  Worth
          looking at if you like the out of the ordinary.  The moving
          force behind this magazine is Daniel Drennan, who seems to have
          suffered from an overdose of radiation from his computer
          monitor ;-).
        - Dan is offering issue 1 of Inquisitor for free except for
          postage ($1.00 in the United States; $2.00 for Canada and
          overseas surface mail; and $3.00 for overseas airmail).  This
          issue contains plans, schematics, and troubleshooting tips for
          putting together a 8052-based microcontroller.  If you're
          thinking of putting together an 8051 system, you might want to
          check this out.
        - Planetarium Station, P.O.Box 132
          New York, NY  10024-0132
        - (212)595-8370
        - Email: inquisitor@echonyc.com
        - $16 per year (4 issues)

    Microcomputer Journal (formerly Computer Craft)
        - programming and construction articles
        - 76 N. Broadway, Hicksville, NY  11801
        - $18.95 one year, foreign $23.00, foreign air mail $76.00

    Midnight Engineering
        - 1700 Washington Ave., Rocky Road, CO  81067
        - (719)254-4553

    MW Media - Product Directories
        - Motorola Microcontroller Tools Directory
          ('94 edition out in 3 weeks)
        - Motorola 68K Source ('94 edition available now)
        - Intel Development Tools Handbook ('95 edition just beginning)
          (survey of commercial development tools for the 8051, 8096,
          and 80186 lines of Intel microprocessors)
        - Embedded Intel 386 Directory (released in Aug '94)
        - Intel 486/Pentium directory (forthcoming in '95)
        - 8051 Product Directory ('94 edition out in 4 weeks)
          (survey of various 8051 products)
        - Hitachi Microcontroller Development Tools Directory
          (out in '95)
        - AMD FusionE86 Directory (out in '95)
        - AMD 29K Directory (pending in '95)
        - Low Power Product Directory (out in '95)
          (3.3. volts and lower)
        - DSP Directory (released in May '94)
        - Multimedia CD (hopefully out in '95)
        - These documents could very well be a "must" if you're into
          serious development using any of these chips.  If you are
          "just" a hobbyist, see how the "other half" lives.
        - FREE to qualified developers
        - MW Media
        - Fairmont Plaza, 50 W. San Fernando, #675, San Jose, CA  95113
        - (408)288-4721   (408)286-4200   FAX: (408)288-4728

    Nuts & Volts Magazine
        - A National Publication for the Buying and Selling of
          Electronic Equipment
        - 430 Princeland Court, Corona, CA  91719
        - Mailed third class, USA only:  $17.00 one year
                                         $31.00 two years
        - Mailed first class, one year only:  $34.00-USA
        - Foreign/Air Mail - $70.00;  Foreign/Surface - $39.00
        - (800)783-4624
        - Email:  74262.3664@Compuserve.com

9.4)  USENET newsgroups

    Various newsgroups frequently have discussions or information on
    various microcontrollers.  Among some of the more useful (especially
    the first 3 newsgroups):

       Microcontrollers figure heavily in robotics projects.  You will
       find a lot of information about the subject in this newsgroup.
       Even if you aren't building a robot, check this newsgroup out.
       Lots of 68hc11 activity, too.

    comp.arch.embedded (great!)
       This is a great newsgroup.  Well targeted discussions on aspects
       of embedded systems and microcontrollers.

    sci.electronics (lots of traffic, but good)
    alt.comp.hardware.homebuilt (too much nonsense on PCs)
       Some good places to find [mostly technical] discussions on
       microcontroller use and implementation.  Most of the participants
       are crazy about "rolling their own", and are eager to share their
       knowledge.  These groups aren't well focused, and many subjects
       that aren't relevant to embedded control are covered here.

       Since embedded systems (controllers/processors) are almost always
       used in real time applications, this group could prove to be
       useful.  Occasional discussions about various microcontroller

       QNX is the leading realtime OS for PCs in terms of market share.
       It is used in high-end embedded systems (16 and 32 bit); set-top
       boxes, automotive industry, banking, telecomms, etc.

       The full line of Motorola 68000 microprocessors is discussed in
       this newsgroup, including the very powerful and advanced embedded
       processors and microcontrollers based on this family.

       This newsgroup covers an old-time favorite, the 6809
       microprocessor, which is commonly used for control applications.
       Motorola 8 bit microprocessors and microcontrollers (6805, 6811,
       etc.) are also discussed in this newsgroup.

       Mostly trends and development are discussed in this newsgroup.
       From time to time you will find a discussion on some technical
       problem or feature.  This newsgroup is usually fairly useless.
       For a while the participants spent most of their time whining
       about the Pentium bug.  Now they're all moaning about Microsoft,
       PowerPCs, and everything else BUT Intel parts.  I propose changing
       the name of this group to alt.crybabies.boo.hoo.hoo.

       Sometimes questions or discussions on different microcontroller
       topics pop up here.  I guess it's the ".misc" that attracts these

       Fuzzy logic is rapidly becoming an increasingly important aspect
       of [embedded] control systems.  This group might very well become
       an important forum for those involved in developing control

       Discussions on Digital Signal Processsing

       Texas Instruments products discussed here

       This forum is for the discussion of control and embedded systems.


9.5)  Internet sources of information on specific microcontrollers

    If you are interested in finding sources of information on a specific
    microcontroller, check out the really fine FAQs ;-) that have been
    compiled for the more popular microcontrollers.

      Subject:  PIC microcontrollers
      Web page:  http://digiserve.com/takdesign
      Maintainer:  Tom Kellett
                   Email: Tom@takdsign.demon.co.uk

      Subject:  8051 microcontrollers
      Newsgroups:  comp.sys.intel
      Archive:  rtfm.mit.edu :  
      Maintainer:  Russ Hersch
                   Email: russ@shani.net

      Subject:  68hc11 microcontrollers
      Newsgroups:  comp.realtime
      Archive:  rtfm.mit.edu :  
      Maintainer:  Robert Boys - Ontario, Canada
                   Email: rboys@best.com
                   Russ Hersch (maintainer emeritus :-)

      Subject:  Motorola 68K microprocessor line
      Newsgroups:  comp.sys.m68k
      Archive:  ftp.ee.ualberta.ca : pub/motorola/general
                ftp.luth.se : /pub/misc/motorola/faq
                file name of archive is m68kfaq?.zip (? is version)
      Comments:  - also includes information on the 683xxx and 68hc16
                 - without a doubt, one of the finest FAQs ever written
                 (well, of course Bob paid me to say this ;-)
      Maintainer:  Robert Boys - Ontario, Canada
                   Email: rboys@best.com

      Subject:  ST6 microcontroller FAQ
      Newsgroups: sci.electronics
      Maintainer:  Emilio Caggiano - caggiano@vm.csata.it
                   Jerry van Kampen - ersicjer@er.ele.tue.nl
                   Leonhard Schneider - ubie@rz.uni-karlsruhe.de

    Several other FAQs have been compiled that address various aspects of
    microcontroller design and implementation.

      Subject:  I2C protocol
      Newsgroups:  sci.electronics
      Comments:    The I2C bus is a simple 2 wire serial interface
                   developed by Philips.  A number of 8051 variants as
                   well as several peripherals include I2C support.
      Maintainer:  Vincent Himpe
                   Email: Vincent.Himpe@ping.be

      Subject:  Robotics
      Newsgroups:  comp.robotics
      Maintainer:  Kevin Dowling
                   Email: nivek@ri.cmu.edu
                   Smail: Carnegie Mellon University
                          The Robotics Institute
                          Pittsburgh, PA 15213

      Subject:  Electronics
      Newsgroups:  sci.electronics
      Comments:  There are a number of FAQs available in this newsgroup
                 on various subjects.  Among some of the subjects covered
                 are:  LCDs, stepper motors, suppliers, etc.

      Subject:  Real-time
      Newsgroups:  comp.realtime, comp.answers, news.answers
      Archive:  rtfm.mit.edu : pub/usenet/comp.realtime
      Maintainer:  Mark Linimon
                       Lonesome Dove Computing Services
                       Roanoke, Virginia
                   Email: linimon@nominil.lonesome.com.

      Subject:  Neural Networks
      Newsgroups:  comp.ai.neural-nets,comp.answers,news.answers
      Archive:  rtfm.mit.edu : pub/usenet/neural-net-faq
      Maintainer:  Lutz Prechelt
                   Email: prechelt@ira.uka.de

      Subject:  Fuzzy Logic
      Newsgroups:  comp.ai.fuzzy,comp.answers,news.answers
      Archive:  rtfm.mit.edu : pub/usenet/fuzzy-logic/
      Maintainer:  Mark Kantrowitz
                   Email: mkant+@cs.cmu.edu

      Subject:  alt.comp.hardware.homebuilt FAQ
      Newsgroups:  alt.comp.hardware.homebuilt
      Comments:  This file contains frequently asked questions (FAQ) and
                 general information pertaining to the newsgroup
      Maintainer:  Mark Sokos (msokos1@gl.umbc.edu)


    This section includes descriptions and references to free
    microcontroller software.  FTP sites and BBSs contain many quality
    packages and code samples for free.  For heavy duty use, you might
    prefer the many commercial packages that are available.  With the
    public domain (or free) stuff, you're usually on your own.  The
    commercial packages usually provide extensive documentation and

    If you are looking for commercial software for the 8051, 68hc11, or
    PIC, then check out the FAQs on these microcontrollers for details on
    what is available.

10.1)  FTP sites

    The following is a list of the anonymous ftp sites that have source
    code and programming languages for various microcontrollers.  There
    are many others that  are not listed here that contains bits and
    pieces.  Usually you can find them using Archie and searching for
    variations on the name of the microntroller you are looking for.

    ftp.pppl.gov (formerly lyman.pppl.gov)
        - this is a great source of 8051 stuff
        /pub/incoming - check this out for new untested/unsorted items

        - this is a new 8051 ftp site

        - good source of stuff the MCS-51 and MCS-96 families
        /pub/mcs51 - various development tools and sample code for the
                     MCS-51 family
        /pub/mcs96 - various development tools and sample code for the
                     MCS-96 family

        - mirror of ftp.intel.com

    freeware.aus.sps.mot.com (Motorola)
        - the ftp site version of the freeware BBS
        - lots of free software for the HC05, HC08, HC11, HC16, 680x0,
          683xx, and PowerPC
        - also see the Web pages in the next section

        - the authoratative source for COP8 infomation
        /pub/COP8 - various develepment tools and sample code for the
                    COP8 family including most application notes

        - /pub/philips
        - Philips "mini ftp site" set up by Phil Wood of Philips
        - lots of 8051 code and programming tools from their BBS

        - send Email message with the word "help" in the subject line to
          learn how to access the archive

        - Circuit Cookbook
        - HUGE archive of all sorts of stuff on the 68hc11 (lots of other
          good stuff too!)
        - you'll have fun mucking around this ftp site, there's piles of
          stuff here

    cherupakha.media.mit.edu (cher.media.mit.edu)
        - HUMONGOUS archive of all sorts of stuff on the 68hc11 including
          the 6.270 robotics project, Mini Board, F1 board, and more
          (lots of other good stuff too!)
        - you'll lose yourself rooting around this ftp site, there's
          piles of stuff here (assemblers, tools, C compilers, plans and
          schematics, and many other items)
        /pub/projects - tools, docs, schematics, etc. for the MIT 6.270
          robotics project using a 68hc11-based development system
        /pub/6811 - software, schematics, etc. for the 68hc11-based F1
        /pub/incoming - various unsorted or new items
        /pub/miniboard - software, docs, schematics, etc. for the 3"x2",
          68hc11-based Mini Board controller

    ftp.funet.fi (nic.funet.fi)
        - this is a good source for various microcontrollers
        /pub/microprocs/ (subdirectories include: 1802, 6805, 8048,
           8051, 8096, PIC and many other microprocessors)

        - many assemblers, utilities, and application notes for the PIC
        - Microchip BBS mirror
        - ftp site of Memec Scandinavia, Microchip's Swedish agent.

        - files provided by local Motorola representative
        /pub (subdirectories include: ibm, dsp96k, dsp56100, dsp56k,
          dsptools, develop, mac, mcu302, mcu332, mcu11, pgmr, mcu16,
          mcu, market, qa, general, m68k, evm, dsp)

        - basic stamp information
        - PIC "C" compiler


        /pub/misc/microchip - PIC information
        /pub/misc/microchip/stamp/mirror - mirror of wpi.wpi.edu
        /pub/languages/assembler - various freeware assemblers

        read the 00readme file first or you'll be lost

    asterix.inescn.pt - FORTH archive

        /mirrors/.hpib0/forth/8051 (mirror of asterix Forth archive)

        /pub/imagecft - prerelease version of ImageCraft C for 68hc11

    info@circellar.com - Email (not ftp)
        - send Email to get information file on services available
        - all Circuit Cellar INK and BYTE related files available

        /biz/mchip - PIC information
        - also see the Web page: http://www.ultranet.com/biz/mchip


        - has information and software for a wide range of
          microprocessors and microcontrollers

        - information on PIC

    ftp.armory.com (Steve Walz)
        - /pub/user/rstevew/8051
        - /pub/user/rstevew/TB8051
        - /pub/user/rstevew/incoming

    ftp.cygnus.com (Jeff Fox)
        - source of information and software on the MuP21 Forth
        /pub/forth - MUP21FTP.ZIP includes a software simulator for
            the MuP21 and and the upcoming F21.
        also see the Web page: http://www.dnai.com/~jfox

        - embedded systems FTP archive

        - ftp site of Parallax
          "Cool PIC development tools & the BASIC Stamp"

    ftp.std.com - Minds-Online ftp site
        - Chock full of compilers, assemblers, code, articles, fuzzy
          logic, and much more.

        - support for Texas Instruments parts

        - mirror of the contents of Texas Instruments BBS

        - Microchip PIC and embedded systems

        - electronics archive

10.2)  Web pages

    Advanced Micro Devices, Embedded Processor Division home page
        - http://www.amd.com/html/products/EPD/EPD.html
        - covers both the 29K and E86 embedded processor lines

    Ada language pages
        - http://sw-eng.falls-church.va.us/AdaIC/
        - http://www.adahome.com/

    AM Research, the Embedded Control Experts
        - http://www.amresearch.com

    Automation and Process Control
        - http://www.ba-karlsruhe.de/automation/home.html

    Bo Eriksson's web page (mostly in Swedish :-(
        - info on tools from IAR, plus interesting links
        - info on H8-series from Hitachi

    Brian Brown's 8051 web page
        - http://www.cit.ac.nz/smac/cbt/hwsys/i8051/default.htm
        - contains Brian Brown's 8051 course
        - lots of other good stuff

    Cera Research web pages
        - Electronic Engineers' Toolbox (home page)
        - MCU/MPU resources
        - Navi-GATOR (embedded dev. tools and chip-specific)

    Chip Directory and Chip Manufacturers (Jaap van Ganswijk)
        - http://www.hitex.com/chipdir           (USA, California)
        - http://www.civil.mtu.edu/chipdir       (USA, Michigan)
        - http://www.leg.ufrj.br/chipdir         (Brasil)
        - http://www.xs4all.nl/~ganswijk/chipdir (The Netherlands)
        - http://bbs.cc.uniud.it/chipdir         (Italy)

    Chipmakers web page (Gary Creager)
        - http://www.scruznet.com/~gcreager/hello5.htm
        - well over 200 semiconductor manufacturers web pages

    Circuit Cellar Ink
        - http://www.circellar.com

    Dallas Semiconductor
        - http://www.dalsemi.com

    Diamond Chip
        - http://www.dchip.com
        - information on their ST62T25 BASIC chip
        - Stefan Ward, Diamond Chip
          Tel +27 (0)12 803-6287
          Fax +27 (0)12 803-4350
          BBS +27 (0)12 803-5683

    Electronic Laboratory of the DAEC Department of Meudon
        - http://formper1.obspm.fr
        - electronics, embedded systems, FPGA, microncontrollers in
          astronomy projects

    Embedded Systems Information (Cera Research)
        - http://www.cera.com

    Forth Interest Group home page
        - http://taygeta.oc.nps.navy.mil/fig_home.html

    French Forth web site
        - http://ourworld.compuserve.com/homepages/mp7
          maintained by Marc Petremann:
             17, allee de la Noiseraie
             F - 93160 NOISY LE GRAND
             Email: 100647.3306@compuserve.com
        - http://ourworld.compuserve.com/homepages/bioforth
          maintained by Gerard SOULA

    Gernsback Web page (Electronics Now, Popular Electronics)
        - http://www.gernsback.com
        - current issue information, recent article related files, FTP
          site, subscription information

    Gregory Pugh's homepage
        - http://sleepy.anest.ufl.edu/~glp/8051.html

    High Tech Horizon
        - http://www.hth.com
        - This web page is in Swedish, but the files are available to all
          in the "Hardware Hackers Filelibrary" at the bottom of the
        - High Tech Horizon, Asbogatan 29 C, S-262 51 Angelholm, SWEDEN
          +46 431 41 00 88   Fax: +46 431 41 00 88
          Email: info@hth.com

        - http://www.hitachi-eu.com/hel/ecg/

    ITU Technologies (ITUTec@aol.com)
        - Microchip PIC and embedded systems
        - http://www.iglou.com/ITU

    Ken Tindell's CAN web pag
        - http://www.nrtt.demon.co.uk/can.html
        - Source code to drive the Intel 82527 CAN controller is
          available: just send e-mail to info@nrtt.demon.co.uk, with
          "Request Intel 82527 drivers" (without the quotes) in the
          subject line.

    MCU Survey
        - http://bip.golana.pub.ro/mcu/survey

    Microchip PIC
        - http://www.ultranet.com/biz/mchip

    Motorola's semiconductor WWW page
        - http://motserv.indirect.com
        - on-line searchable Master Selection Guide and OEM Price Book
        - 'MFax' service to request all kinds of data sheets
        - a bunch of other cool stuff

    Motorola's microcontroller WWW page
        - http://freeware.aus.sps.mot.com/index.html
        - the WWW version of the freeware BBS
        - lots of free software for the HC05, HC08, HC11, HC16, 680x0,
          683xx, and PowerPC

    MuP21 Forth microcontroller
        - http://www.dnai.com/~jfox
        - information and software on the MuP21 Forth uC

    Parallax Inc. web page
        - http://www.parallaxinc.com
        - "Cool PIC development tools & the BASIC Stamp"

    Peter H. Anderson's web site
        - http://www.access.digex.net/~pha
        - nice site, lots of PIC stuff and interfacing plans
        - Peter H. Anderson
          Dept of Electrical Engineering
          Morgan State University

    POLIS web site
        - POLIS offers an integrated interactive environment for
          specification, co-simulation, formal verification, and
          synthesis of embedded systems implemented as a mix of hardware
          and software components.
        - http://www-cad.eecs.berkeley.edu/Respep/Research/hsc/abstract.html
          Most of the information about POLIS, including pointers to
          source and object code (for various CPUs and OSes) is available
          at this WEB site
        - If you are interested, but do not have WEB access, contact
          them at: polis@ic.eecs.berkeley.edu.

    QNX realtime website
        - http://www.qnx.com

    Scrumpel 68hc11 web page
        - http://www.stack.urc.tue.nl/~hcc6811

    Texas Instruments
        - http://www.ti.com/sc/docs/micro/home.htm

        - http://www.eskimo.com/~zchris
        - 68hc11 information and support for their line of boards

10.3)  BBSs

    The following BBSs have 8051 information:

    Circuit Cellar, Inc.
        - contains code from their magazine articles and from the
          original Circuit Cellar articles in Byte magazine, also
          contains many other interesting items
        - The BBS is mentioned in the masthead of each issue (on the
          table of contents page).  Excerpts from the BBS appear in Ken
          Davidson's ConnecTime column in every issue with a description
          of how to access the system at the end of every column.
        - (203)871-1988
        - Voice: (203)875-2751
        - Fax: (203)872-2204

    Dunfield Development Systems
        - support for their Micro-C C compiler and development tools
        - includes a lot of nice goodies
        - (613) 256-6289

    ED Teck. Pubs BBS
        - run by Fred Eady who writes for hobbyist magazines
        - good source of information on the PIC
        - (407)454-3198

    Electronics Now
        - contains code from their magazine articles
        - (516)293-2283

    Intel American Marketing Applications Support Bulletin Board System
        - 16 lines, hi-speed modems (14.4K)
        - Lots of useful info and files (including design examples)
        - Full ANSI-BBS with color is recommended, but support for just
          about all terminal types is provided
        - 916-356-3600 (24 hours)
          Auto config: 1200 thru 14.4K Baud
          8 data bits, no parity, 1 stop

    Iota Systems, Inc.
        - Support for their line of hardware and software products
        - (702)831-4732

    Jens Holm's electronics BBS:
        - one of a number of BBSs that are networked over most of the
          industrial part of Europe
        - +45-86-510356 (Denmark)
        - distributes all shareware and freeware software which
          relates to electronics
        - system administrator - Jens Holm
          jholm@bjarke.nrg.dtu.dk or Jens.holm@asgaard.dk

    Don Lekei BBS
        - support for the PIC line of microcontrollers
        - (604)597-3479 (Canada)

    Massilia Underground BBS (Marseille, France)
        - +33-91794120
        - fidonet 2:323/25
        - not a commercial BBS
        - microcontroller related stuff (assemblers, debuggers,
          boards, etc), some 8051 stuff
        - everything coming in is tested

    Microchip BBS
        - support for the PIC line of microcontrollers
        - Contact by dialing the same number you would use to get to
          Compuserve at 19200,n,8,1, except that you press + at the
          (garbage) prompt, followed by MCHIPBBS as the host (instead of

    Micro Computer Control Corporation
        - (609)466-4117

    Motorola (Austin Texas) BBS
        - terrific, has piles of stuff, only some of which is on
        - (512) 891-3733 (Austin, Texas)
        - V.32 9600 Baud modems w/ MNP-5
        - 8 Data Bits, No Parity, 1 Stop Bit.

    Other Motorola BBSs:
        - Munich, Germany:  49-89-92103-111  (2400 baud)
        - Stuttgart, Germany:  49-7031-275496  (19200 baud)
        - San Diego, California:  (619) 279-3907
        - Toronto, Ontario, Canada:  (416) 497-8989

    National Semiconductor COP8 BBS
        - (800)672-6427
        - worldwide telnet to nscmicro.national.com

    Protel (Microchip PIC software support)
        - (408)243-0125

    Parallax Inc.
        - (916)624-7101

    Philips Semiconductor (parent company of Signetics)
        - support for: standard logic, programmable logic,
          in-car electronics (planned), 8 and 16 bit microcontrollers,
          I2C software, third party software, discrete semiconductors,
          cross assemblers (general), RF (planned)
        - PHIBBS is located in the Netherlands: +31-40-721102
        - maximum 14400 baud / V42bis
        - 24 hours a day available
        - Help desk: +31-40-722749  (9.00 AM - 16.00 PM CET)

    Philips Semiconductors (Signetics)
        - support for their 8051 variants
        - contains many good source code items
        - partially mirrored on ftp.pppl.gov and nic.funet.fi
        - (800)451-6644 or (408)991-2406

    Texas Instruments microcontroller BBS
        - (713)274-3700

10.4)  Mailing Lists

        - for information, send empty message to listserv@hipp.etsu.edu
        - to join, send the message "subscribe mc68hc11 your_real_name"
          to listserv@hipp.etsu.edu

    Basic Stamp
        - to join, send the message "subscribe stamp-list" to

    GCC compilers for embedded systems
        - to join, send the message "subscribe crossgcc "
          to majordomo@first.gmd.de
        - for those who are building a cross gcc compiler for an
          embedded processor/system

    Imagecraft C
        - to join, send the message "subscribe icc11-list" to

        - One mailing list is for announcing significant postings on the
          Minds-Online ftp site.
        - Another MODERATED mailing list will carry messages from real
          engineers who are working on designs slated for volume
          production.  "No tire-kickers, no students, no academics, no
          sleazy something-for-nothing ripoff artists, no hobbyists, and
          no totally lost people will be able to post e-mail."  (Uh, it
          looks like that sort of leaves out yours truly, I certainly
          belong in several, if not most, of those categories).
        - to join, send the message "subscribe" to the email address:

    Mini Board and 6.270 board (68hc11)
        - send a message containing the word "help" for directions to
        - mailing list address:  robot-board@oberon.com
        - maintainer:  gkulosa@oberon.com

    Parallel Performance Group (PPG)
        - series of monthly newletters on high-tech software topics
        - for information send any e-mail to info@ppgsoft.com

    Philips Newsletter
        - send Email with "subscribe" in the subject field to
        - news, views, and articles (contributions welcome)
    Philips Developers Forum
        - send an Email message with the word "subscribe" in the subject
          to Philips-forum-request@InetBSystems.us.com
        - technical discussions between engineers and developers

        - to subscribe, send email to listserv@mitvma.mit.edu
        - send the message "SUB PICLIST" for standard subscription
        - send the message "SUB PICDIGEST" to receive digested mailings
        - list address is: PIC@mitvma.mit.edu


    Major manufacturers and distributors are the main (and most
    expensive) source for acquiring microcontroller parts.

    A good number of firms have surplus bargains on microcontrollers and
    other parts you might need for your projects. Among some of the
    better ones:

    All Electronics
        - http://www.allcorp.com
        - lots of great surplus items
        - nice catalog available in PDF

        - http://www.alltronics.com
        - good selection of interesting surplus items
        - large selection of standard chips and components
        - latest advertisements available in PDF
        - update pages from catalog available in PDF

    BG Micro
        - http://www.bgmicro.com
        - large selection of standard chips and components
        - much of their catalog available in PDF

    Debco Electronics
        - http://www.debcom.com
        - piles of chips, parts, components, ham gear, computer stuff
        - Electronics Experimentors Journals (highly recommended!)

    Herbach and Rademan
         - http://www.herbach.com
         - great catalog
         - LOTS of stuff for robotics projects

    Mendelson Electronics
        - http://www.meci.com
        - on-line ordering possible, but IMHO their web site is difficult
          to navigate

        - http://www.timeline.com
        - well-known and reliable source for surplus LCD displays
        - interesting surplus bargains


I disclaim everything.  The contents of this article might be totally
inaccurate, inappropriate, misguided, or otherwise perverse - except for
my name (hopefully I got that right).

Copyright  1997 by CPU Technologies / Microcontroller.com, all rights reserved.
Original Copyright  1997 by Russ Hersch.
This FAQ may be posted to any USENET newsgroup, on-line service, or BBS
  as long as it is posted in its entirety and includes this copyright
This FAQ may not be distributed for financial gain.
This FAQ may not be included in commercial collections or compilations
   without express permission from the author.



Cores   |  Tools  |  App Notes  |  References  |  Semiconductors  |  Tutorials  |  What's Inside
Editorials  |  News  |  Marketplace  |  Events  |  Jokes  |  Contact  |  CPU Technologies  |  Privacy Statement

Waddya think of Microcontroller.com? Email us your comments!

* * * Legal Gibberish * * *
Copyright 2000 CPU Technologies. All Rights Reserved. Information provided "as-is" without warranty. Please see details.
Contact Microcontroller.com for usage and copy permission.