Motorola DSP56000 Manual page 499

MPY
MPY
Instruction Fields 1:
∗
S1 S2 Q Q Q
X0 X0 0 0 0
Y0 Y0 0 0 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
Timing: 2+mv oscillator clock cycles
Memory: 1+mv program words
Example 2:
:
MPY X1, #9, A
:
Before Execution
X1
A
$00:000000:000000
Explanation of Example 2: The content of X1 is multiplied by 2
placed in the A accumulator. The net effect of this operation is to divide the content of
9
X1 by 2 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.
A - 230
INSTRUCTION DESCRIPTIONS
Signed Multiply
Sign k
+ 0
– 1
∗
S2 combinations are valid. X1
;
$654321
INSTRUCTION SET DETAILS
D d
A 0
B 1
∗
X1 and Y1
After Execution
X1
$654321
A
$00:0032A1:908000
∗
Y1 are not valid.
-9
and the result is
MOTOROLA