HCS12 datasheet(351/452 Pages) FREESCALE

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S12CPUV2 Reference Manual, Rev. 4.0

Freescale Semiconductor

351

The special cases shown here represent abnormal membership function

definitions. The explanations describe how the specific algorithm in the

CPU12 resolves these unusual cases. The results are not all intuitively

obvious, but rather fall out from the specific algorithm. Remember, these

cases should not occur in a normal system.

9.4.2.1 Abnormal Membership Function Case 1

This membership function is abnormal because the sloping sides cross

below the $FF cutoff level. The flag_d12n signal forces the membership

function to evaluate to $00 everywhere except from point_1 to point_2.

Within this interval, the tentative values for grade_1 and grade_2 calculated

in cycle 3 fall on the crossed sloping sides. In step 4a, grade gets set to the

grade_2 value, but in 4b this is overridden by the grade_1 value, which ends

up as the result of the MEM instruction. One way to say this is that the result

follows the left sloping side until the input passes point_2, where the result

goes to $00.

Figure 9-6. Abnormal Membership Function Case 1

If point_1 was to the right of point_2, flag_d12n would force the result to be

$00 for all input values. In fact, flag_d12n always limits the region of interest

to the space greater than or equal to point_1 and less than or equal to

point_2.

MEMORY DEFINITION: $60, $80, $04, $04; point_1, point_2, slope_1, slope_2

GRAPHICAL REPRESENTATION

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