HCS12 datasheet(67/452 Pages) FREESCALE

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S12CPUV2 Reference Manual, Rev. 4.0

Freescale Semiconductor

5.15 Fuzzy Logic Instructions

The CPU12 instruction set includes instructions that support efficient

processing of fuzzy logic operations. The descriptions of fuzzy logic

instructions given here are functional overviews. Table 5-13 summarizes

the fuzzy logic instructions. Refer to Section 9. Fuzzy Logic Support for

detailed discussion.

5.15.1 Fuzzy Logic Membership Instruction

The membership function (MEM) instruction is used during the fuzzification

process. During fuzzification, current system input values are compared

against stored input membership functions to determine the degree to which

each label of each system input is true. This is accomplished by finding the

y value for the current input on a trapezoidal membership function for each

label of each system input. The MEM instruction performs this calculation

for one label of one system input. To perform the complete fuzzification task

for a system, several MEM instructions must be executed, usually in a

program loop structure.

5.15.2 Fuzzy Logic Rule Evaluation Instructions

The MIN-MAX rule evaluation (REV and REVW) instructions perform

MIN-MAX rule evaluations that are central elements of a fuzzy logic

inference program. Fuzzy input values are processed using a list of rules

from the knowledge base to produce a list of fuzzy outputs. The REV

instruction treats all rules as equally important. The REVW instruction

allows each rule to have a separate weighting factor. The two rule

evaluation instructions also differ in the way rules are encoded into the

knowledge base. Because they require a number of cycles to execute, rule

evaluation instructions can be interrupted. Once the interrupt has been

serviced, instruction execution resumes at the point the interrupt occurred.

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