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Copyright Ó 2001 Microcontroller.com. All Rights Reserved.
March 2001
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A high clock speed facilitates brute-forcing control and signal tasks while still
maintaining real-time performance.
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A register-based architecture facilitates moving data through the stream
A register-based architecture is certainly preferable to an accumulator-based
architecture. Back when the cost of silicon was much more expensive and process
technology sizes were specified in whole numbers, an accumulator was an expensive
piece of silicon real estate. About the time microcontrollers started being fabricated in
0.8m, the first general market register-based microcontrollers were introduced. This
alleviated the bottleneck of the accumulator and allowed more effective movement of
data.
However, despite these enhancements, the inability to fetch two pieces of data
simultaneously, plus the lack of a MAC (found in only a few microcontrollers) obviously
limits the functionality of most microcontrollers when processing analog data and
restricts it to relatively slow to medium duty arithmetic processing.
Simple signal processing functions that can be performed by some 8- and 16-bit
microcontrollers include:
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PID filtering (motor control)
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2400 baud FSK modem
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Caller ID detection
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DTMF encoding/decoding
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Low tap FIR filter
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Video synch
In each situation, real-time control is required in the form of input switch or status
management, and in many cases a user display also needs to be managed.
DC motor control, including industrial applications and robotics, is especially considered
to be a viable target for dual functionality processing. Brushless motors are gradually
replacing commutation motors as they are smaller, less expensive and do not require as
much maintenance. Moreover, brushless motors are much lower EMI than commutation
motors. The math functions required for the precision control of motors are more
applicable to a DSP's hardware than a conventional microcontroller.
REAL-TIME CONTROL IN A DSP
In the past, a DSP would never be considered for a microcontroller application because,
besides having excessive processing power and insufficient on-chip peripherals, DSPs
were simply too expensive for these applications. With shrinks to sub-micron and
increased on-chip integration on many DSPs, this is changing.
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