HCS12 datasheet(261/452 Pages) FREESCALE

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Glossary

S12CPUV2 Reference Manual, Rev. 4.0

Freescale Semiconductor

261

Index register X points to the element in the rule list that is being evaluated.

X is automatically updated so that execution can resume correctly if the

instruction is interrupted. When execution is complete, X points to the

address after the $FFFF separator at the end of the rule list.

Index register Y points to the weighting factor being used. Y is automatically

updated so that execution can resume correctly if the instruction is

interrupted. When execution is complete, Y points to the last weighting

factor used. When weighting is not used (C = 0), Y is not changed.

Accumulator A holds intermediate results. During antecedent processing, a

MIN function compares each fuzzy input to the value stored in A and writes

the smaller of the two to A. When all antecedents have been evaluated, A

contains the smallest input value. For unweighted evaluation, this is the

truth value used during consequent processing. For weighted evaluation,

the value in A is multiplied by the quantity (Rule Weight + 1) and the upper

eight bits of the result replace the content of A. Accumulator A must be

initialized to $FF for the MIN function to evaluate the inputs of the first rule

correctly. For subsequent rules, the value $FF is automatically written to A

when an $FFFE marker is encountered. At the end of execution,

accumulator A holds the truth value for the last rule.

The V status bit signals whether antecedents (0) or consequents (1) are

being processed. V must be initialized to 0 for processing to begin with the

antecedents of the first rule. Once execution begins, the value of V is

automatically changed as $FFFE separators are encountered. At the end of

execution, V should equal 1, because the last element before the $FF end

marker should be a rule consequent. If V is equal to 0 at the end of

execution, the rule list is incorrect.

Fuzzy outputs must be cleared to $00 before processing begins in order for

the MAX algorithm used during consequent processing to work correctly.

Residual output values would cause incorrect comparison.

Refer to Section 9. Fuzzy Logic Support for details.

REVW Fuzzy Logic Rule Evaluation (Weighted)

(Continued)

REVW

HCS12 Datasheet(PDF) 261 Page - Freescale Semiconductor, Inc