INSTRUCTION DESCRIPTIONS
A - 230 INSTRUCTION SET DETAILS MOTOROLA
Instruction Fields 1:
S1∗S2 Q Q Q Sign k D d
X0 X0 0 0 0 + 0 A 0
Y0 Y0 0 0 1 – 1 B 1
X1 X0 0 1 0
Y1 Y0 0 1 1
X0 Y1 1 0 0
Y0 X0 1 0 1
X1 Y0 1 1 0
Y1 X1 1 1 1
Note: Only the indicated S1∗S2 combinations are valid. X1∗X1 and Y1∗Y1 are not valid.
Timing: 2+mv oscillator clock cycles
Memory: 1+mv program words
Example 2: :
MPY X1, #9, A ;
:
Explanation of Example 2: The content of X1 is multiplied by 2-9 and the result is
placed in the A accumulator. The net effect of this operation is to divide the content of
X1 by 29 and place the result in the accumulator. An alternate interpretation is that X1 is
right shifted 9 places and filled with the sign bit (0 for a positive number and 1 for a neg-
ative number) and then the result is placed in the accumulator.
MPY Signed Multiply
MPY
Before Execution After Execution
X1 $654321
A A
$00:000000:000000 $00:0032A1:908000
$654321
X1