Texas Instruments MSP430x1xx - Manual (Page 400)

Running Title—Attribute Reference
B-50
Example R5 is shifted right one position. The MSB retains the old value. It operates
equal to an arithmetic division by 2.
RRA R5 ; R5/2 –> R5
; The value in R5 is multiplied by 0.75 (0.5 + 0.25).
;
PUSH R5 ; hold R5 temporarily using stack
RRA R5 ; R5
×
0.5 –> R5
ADD @SP+,R5 ; R5
×
0.5 + R5 = 1.5
×
R5 –> R5
RRA R5 ; (1.5
×
R5)
Ч
0.5 = 0.75
Ч
R5 –> R5
......
......
; OR
;
RRA R5 ; R5
×
0.5 –> R5
PUSH R5 ; R5
×
0.5 –> TOS
RRA @SP ; TOS
Ч
0.5 = 0.5
Ч
R5
Ч
0.5 = 0.25
Ч
R5 –> TOS
ADD @SP+,R5 ; R5
×
0.5 + R5
Ч
0.25 = 0.75
Ч
R5 –> R5
......
Example The low byte of R5 is shifted right one position. The MSB retains the old value.
It operates equal to an arithmetic division by 2.
RRA.B R5 ; R5/2 –> R5: operation is on low byte only
; High byte of R5 is reset
; The value in R5 (low byte only) is multiplied by 0.75 (0.5 + 0.25).
;
PUSH.B R5 ; hold low byte of R5 temporarily using stack
RRA.B R5 ; R5
×
0.5 –> R5
ADD.B @SP+,R5 ; R5
×
0.5 + R5 = 1.5
×
R5 –> R5
RRA.B R5 ; (1.5
×
R5)
Ч
0.5 = 0.75
Ч
R5 –> R5
......
; OR
;
RRA.B R5 ; R5
×
0.5 –> R5
PUSH.B R5 ; R5
×
0.5 –> TOS
RRA.B @SP ;TOS
Ч
0.5 = 0.5
Ч
R5
Ч
0.5 = 0.25
Ч
R5 –> TOS
ADD.B @SP+,R5 ; R5
×
0.5 + R5
Ч
0.25 = 0.75
Ч
R5 –> R5
......