Instruction Set
3-60
RISC 16-Bit CPU
RRA[.W]
Rotate right arithmetically
RRA.B
Rotate right arithmetically
Syntax
RRA
dst or
RRA.W
dst
RRA.B
dst
Operation
MSB −> MSB, MSB −> MSB−1, ... LSB+1 −> LSB,
LSB −> C
Description
The destination operand is shifted right one position as shown in Figure 3−16.
The MSB is shifted into the MSB, the MSB is shifted into the MSB−1, and the
LSB+1 is shifted into the LSB.
Figure 3−16. Destination Operand—Arithmetic Right Shift
15
0
15
0
C
Byte
Word
Status Bits
N: Set if result is negative, reset if positive
Z: Set if result is zero, reset otherwise
C: Loaded from the LSB
V: Reset
Mode Bits
OSCOFF, CPUOFF, and GIE are not affected.
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)
×
0.5 = 0.75
×
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
PUSH.B
R5
; R5
×
0.5 −> TOS
RRA.B
@SP
; TOS
×
0.5 = 0.5
×
R5
×
0.5 = 0.25
×
R5 −> TOS
ADD.B
@SP+,R5
; R5
×
0.5 + R5
×
0.25 = 0.75
×
R5 −> R5
......
Summary of Contents for MSP430x4xx Family
Page 1: ...MSP430x4xx Family 2007 Mixed Signal Products User s Guide SLAU056G ...
Page 2: ......
Page 6: ...vi ...
Page 114: ...3 76 RISC 16 Bit CPU ...
Page 304: ...5 20 FLL Clock Module ...
Page 340: ...7 8 Supply Voltage Supervisor ...
Page 348: ...8 8 16 Bit Hardware Multiplier ...
Page 372: ...9 24 32 Bit Hardware Multiplier ...
Page 400: ...10 28 DMA Controller ...
Page 428: ...13 10 Basic Timer1 ...
Page 466: ...15 24 Timer_A ...
Page 522: ...17 30 USART Peripheral Interface UART Mode ...
Page 544: ...18 22 USART Peripheral Interface SPI Mode ...
Page 672: ...23 12 Comparator_A ...
Page 692: ...24 20 LCD Controller ...
Page 746: ...26 28 ADC12 ...