HCS12 datasheet(260/452 Pages) FREESCALE

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Instruction Glossary

S12CPUV2 Reference Manual, Rev. 4.0

260

Freescale Semiconductor

Operation:

MIN-MAX Rule Evaluation with Optional Rule Weighting

Description:

REVW performs either weighted or unweighted evaluation of a list of rules,

using fuzzy inputs to produce fuzzy outputs. REVW can be interrupted, so it

does not adversely affect interrupt latency.

For REVW to execute correctly, each rule in the knowledge base must

consist of a table of 16-bit antecedent pointers followed by a table of 16-bit

consequent pointers. The value $FFFE marks boundaries between

antecedents and consequents, and between successive rules. The value

$FFFF marks the end of the rule list. REVW can evaluate any number of

rules with any number of inputs and outputs.

Setting the C status bit enables weighted evaluation. To use weighted

evaluation, a table of 8-bit weighting factors, one per rule, must be stored in

memory. Index register Y points to the weighting factors.

Beginning with the address pointed to by the first rule antecedent, REVW

evaluates each successive fuzzy input value until it encounters an $FFFE

separator. Operation is similar to that of a MINA instruction. The smallest

input value is the truth value of the rule. Next, if weighted evaluation is

enabled, a computation is performed, and the truth value is modified. Then,

beginning with the address pointed to by the first rule consequent, the truth

value is compared to each successive fuzzy output value until another

$FFFE separator is encountered; if the truth value is greater than the current

output value, it is written to the output. Operation is similar to that of a MAXM

instruction. Rules are processed until an $FFFF terminator is encountered.

Perform these set up operations before execution:

• X must point to the first 16-bit element in the rule list.

• A must contain the value $FF, and the CCR V bit must = 0

(LDAA #$FF places the correct value in A and clears V).

• Clear fuzzy outputs to 0s.

• Set or clear the CCR C bit. When weighted evaluation is enabled,

Y must point to the first item in a table of 8-bit weighting factors.

REVW Fuzzy Logic Rule Evaluation (Weighted) REVW

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