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Embedded Web Server for the CR16
National Semiconductor
Jeff Wright
3
An Embedded Web Server for National Semiconductor’s 16-bit
Microcontroller – The CR16MCS9 CannonBall
What datagrams may come…
Abstract:
These days it seems, everybody and their brother is talking about the need of becoming “Internet
aware” - a new catch phrase sounding eerily similar to something said in Eden some time ago.  The
explosive growth and appeal of the Internet has everyone scrambling to get onboard, or be thought
of as somehow “20th century”.  Today, Internet accessibility in one form or another, if not an a
priori requirement, is at least a highly desirable option in many embedded applications.  Previously
the sole domain of mainframes, PCs, and workstations, TCP/IP stacks and other networking
applications are now being written by the dozens for embedded microprocessors and
microcontrollers, providing them the smarts to hook into the “matrix”.  This article will examine one
such TCP/IP stack and Web server implemented on National Semiconductor’s CannonBall 16-bit
RISC microcontroller.  We’ll also seek to resonate some understanding of the basic issues one needs
to consider when deciding on which approach is best suited for their embedded Internet
application. 
Introduction:
The rapid advances in semiconductor technology throughout the last decade of the 20th century
have enabled the development of powerful new microprocessors and microcontrollers, bringing the
embedded world computational power previously found only in mainframes, supercomputers, and
idiot savants like the Rainman.  RISC architectures, previously untenable in a cost sensitive
embedded word (due to their thirst for expensive memory), have now been adopted as somewhat
standard fare.  National Semiconductor’s CompactRISC is one such architecture, having at once the
power necessary to run the networking software to connect your embedded application to the
Internet, and the memory efficiency still requisite in the embedded world.   
Discussion:
Among the myriad of embedded Internet solutions being touted today, most fall neatly into one of
five fundamental groups:  
1.
Embedding a fully functional (or nearly so), third party TCP/IP stack into your application,
enabling direct Internet access…
2.
Using a third party’s external TCP/IP device, such as NetSilicon’s Net+ARM™ solutions…
3.
Writing your own TCP/IP stack, or some functional subset thereof…
4.
Using your own, or a third party’s, “lightweight”, proprietary communication protocol to talk with
an external gateway device, which is itself connected to the Internet (e.g. EmWare)…
5.
Everything else – for those which don’t fall that neatly.
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