INSTRUCTION DESCRIPTIONS
A - 28 INSTRUCTION SET DETAILS MOTOROLA
Operation: Assembler Syntax:
S+2∗D➞D (parallel move) ADDL S,D (parallel move)
Description: Add the source operand S to two times the destination operand D and
store the result in the destination accumulator. The destination operand D is arithmeti-
cally shifted one bit to the left, and a zero is shifted into the LS bit of D prior to the addi-
tion operation. The carry bit is set correctly if the source operand does not overflow as a
result of the left shift operation. The overflow bit may be set as a result of either the shift-
ing or addition operation (or both). This instruction is useful for efficient divide and deci-
mation in time (DIT) FFT algorithms.
Example: :
ADDL A,B #$0,R0 ;A+2∗B➞B, set up addr. reg. R0
:
Explanation of Example: Prior to execution, the 56-bit accumulator contains the value
$00:000000:000123, and the 56-bit B accumulator contains the value
$00:005000:000000. The ADDL A,B instruction adds two times the value in the B accu-
mulator to the value in the A accumulator and stores the 56-bit result in the B accumula-
tor.
ADDL Shift Left and Add Accumulators ADDL
Before Execution After Execution
AA
$00:000000:000123
BB
$00:005000:000000 $00:00A000:000123
$00:000000:000123