INSTRUCTION DESCRIPTIONS
A - 36 INSTRUCTION SET DETAILS MOTOROLA
Assembler Syntax: ASL D (parallel move)
Description: Arithmetically shift the destination operand D one bit to the left and store
the result in the destination accumulator. The MS bit of D prior to instruction execution is
shifted into the carry bit C and a zero is shifted into the LS bit of the destination accumu-
lator D. If a zero shift count is specified, the carry bit is cleared. The difference between
ASL and LSL is that ASL operates on the entire 56 bits of the accumulator and therefore
sets the V bit if the number overflowed.
Example: :
ASL A (R3)– ;multiply A by 2, update R3
:
Explanation of Example: Prior to execution, the 56-bit A accumulator contains the
value $A5:012345:012345. The execution of the ASL A instruction shifts the 56-bit value
in the A accumulator one bit to the left and stores the result back in the A accumulator.
ASL Arithmetic Shift Accumulator Left ASL
55 47 23 0
C0 (parallel move)
Operation:
Before Execution After Execution
AA
$A5:012345:012345
SR SR
$0300 $0373
$4A:02468A:02468A