INSTRUCTION DESCRIPTIONS
A - 156 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: :
MACR -Y0, #10, B ;
:
Explanation of Example 2: The content of Y0 ($654321) is negated, multiplied by 2-10,
added to the content of the B accumulator ($00:100000:000000), placed in the B accu-
mulator and then rounded to a single precision number (24 bits in B1). The net effect of
this operation is to negate the content of Y0, divide the result by 210 and add the result
to the accumulator. An alternate interpretation is that Y0 is negated, right shifted 10
places, filled with the sign bit (0 for a positive number and 1 for a negative number), the
result is added to the accumulator and then rounded to a single precision number.
MACR Signed Multiply-Accumulate and Round MACR
Before Execution After Execution
Y0 $654321
B B
$00:100000:000000 $00:0FE6AF:000000
$654321
Y0