Motorola DSP56000 Manual page 500

MPYR
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:
:
MPYR -Y1, #14, B
:
Before Execution
Y1
B
$00:000000:000000
Explanation of Example 2: The content of Y1 is negated, multiplied by 2
a single precision number (24 bits in B1) and placed in the B accumulator. The net effect
of this operation is negate the content of Y1 and divide the result by 2
in the accumulator and then round to a single precision number. An alternate interpreta-
tion is that X1 is negated and placed in the accumulator, right shift ed 14 places, filled
with the sign bit (0 for a positive number and 1 for a negative number) and then rounded
to a single precision number.
A - 234
INSTRUCTION DESCRIPTIONS
Signed Multiply and Round
Sign k
+ 0
– 1
∗
S2 combinations are valid. X1
;
$654321
INSTRUCTION SET DETAILS
D d
A 0
B 1
∗
X1 and Y1
After Execution
Y1
$654321
B
$FF:FFFE6B:000000
MPYR
∗
Y1 are not valid.
-14
, rounded to
14
, place the result
MOTOROLA