HCS12 datasheet(338/452 Pages) FREESCALE

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S12CPUV2 Reference Manual, Rev. 4.0

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Freescale Semiconductor

Other instructions that are useful for custom fuzzy logic programs include:

• MINA (place smaller of two unsigned 8-bit values in accumulator A)

• EMIND (place smaller of two unsigned 16-bit values in

accumulator D)

• MAXM (place larger of two unsigned 8-bit values in memory)

• EMAXM (place larger of two unsigned 16-bit values in memory)

• TBL (table lookup and interpolate)

• ETBL (extended table lookup and interpolate)

• EMACS (extended multiply and accumulate signed 16-bit by 16-bit to

32-bit)

For higher resolution fuzzy programs, the fast extended precision math

instructions in the CPU12 are also beneficial. Flexible indexed addressing

modes help simplify access to fuzzy logic data structures stored as lists or

tabular data structures in memory.

The actual logic additions required to implement fuzzy logic support in the

CPU12 are quite small, so there is no appreciable increase in cost for the

typical user. A fuzzy inference kernel for the CPU12 requires one-fifth as

much code space and executes almost 50 times faster than a comparable

kernel implemented on a typical midrange microcontroller.

9.2 Fuzzy Logic Basics

This is an overview of basic fuzzy logic concepts. It can serve as a general

introduction to the subject, but that is not the main purpose. There are a

number of fuzzy logic programming strategies. This discussion

concentrates on the methods implemented in the CPU12 fuzzy logic

instructions. The primary goal is to provide a background for a detailed

explanation of the CPU12 fuzzy logic instructions.

In general, fuzzy logic provides for set definitions that have fuzzy

boundaries rather than the crisp boundaries of Aristotelian logic. These sets

can overlap so that, for a specific input value, one or more sets associated

with linguistic labels may be true to a degree at the same time. As the input

varies from the range of one set into the range of an adjacent set, the first

set becomes progressively less true while the second set becomes

progressively more true.

Fuzzy logic has membership functions which emulate human concepts like

“temperature is warm”; that is, conditions are perceived to have gradual

boundaries. This concept seems to be a key element of the human ability to

HCS12 Datasheet(PDF) 338 Page - Freescale Semiconductor, Inc