Texas Instruments TMS320C28x, Reference Manual

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ASR AX,#1...16
6-53
ASR AX,#1...16 Arithmetic Shift Right
SYNTAX OPTIONS OPCODE OBJMODE RPT CYC
ASR AX,#1...16
1111 1111 101A SHFT
X − 1
Operands AX Accumulator high (AH) or accumulator low (AL) register
1 0 16 Shift value
Description Perform an arithmetic right shift on the content of the specified AX register (AH
or AL) by the amount given in the “shift value” field. During the shift, the value
is sign extended and the last bit to be shifted out of the AX register is stored in
the carry status flag bit:
SIGN
C
AX
AX
Discard
other bits
Right shift
(Immediate value)
Last bit out
Flags and
Modes
N
After the shift, if bit 15 of AX is 1 then the negative flag bit is set; otherwise it is
cleared.
Z After the shift, if AX is 0, then the Z bit is set; otherwise it is cleared.
C The last bit to be shifted out of AH or AL is stored in C.
Repeat This instruction is not repeatable. If this instruction follows the RPT
instruction, it resets the repeat counter (RPTC) and executes only once.
Example
; Calculate signed value: VarC = (VarA + VarB) >> 2
MOV AL,@VarA ; Load AL with contents of VarA
ADD AL,@VarB ; Add to AL contents of VarB
ASR AL,#2 ; Scale result by 2
MOV @VarC,AL ; Store result in VarC