INSTRUCTION DESCRIPTIONS
A - 234 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:
:
MPYR -Y1, #14, B ;
:
Explanation of Example 2:
The content of Y1 is negated, multiplied by 2
-14
, rounded to
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
14
, place the result
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.
Before Execution After Execution
Y1 $654321
B B
$00:000000:000000 $FF:FFFE6B:000000
$654321
Y1
MPYR Signed Multiply and Round MPYR