Motorola DSP56000 Manual page 421

MAC
Timing: 2+mv oscillator clock cycles
Memory: 1+mv program words
Example 2:
:
MAC X0, #3, A
:
Before Execution
X0
A
$00:100000:000000
Explanation of Example 2: The content of X0 ($654321) is multiplied by 2
added to the content of the A accumulator ($00:100000:000000). The result is then
placed in the A accumulator. The net effect of this operation is to divide the content of
3
X0 by 2 and add the result to the accumulator. An alternate interpretation is that X0 is
right shifted 3 places and filled with the sign bit (0 for a positive number and 1 for a neg-
ative number) and then the result is added to the accumulator.
Instruction Format 2:
±
MAC ( )S,#n,D
Opcode 2:
23
0 0 0 0
Instruction Fields:
S Q Q
Y1 0 0
X0 0 1
Y0 1 0
X1 1 1
A - 152
INSTRUCTION DESCRIPTIONS
Signed Multiply-Accumulate
;
$654321
16 15
0 0 0 1 0 0 0
Sign k D
+ 0 A
– 1 B
INSTRUCTION SET DETAILS
After Execution
X0
A
$00:1CA864:200000
8 7
s s s s s 1 1
d
0
1
MAC
$654321
-3
and then
0
Q Q d k 1 0
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