Texas Instruments MSP430x1xx User Manual
Page 409
Instruction Set Overview
B-59
Instruction Set Description
SXT
Extend Sign
Syntax
SXT
dst
Operation
Bit 7 –> Bit 8 ......... Bit 15
Description
The sign of the low byte is extended into the high byte as shown in Figure B–11.
Status Bits
N: Set if result is negative, reset if positive
Z: Set if result is zero, reset otherwise
C: Set if result is not zero, reset otherwise (.NOT. Zero)
V: Reset
Mode Bits
OscOff, CPUOff, and GIE are not affected.
Figure B–11. Destination Operand Sign Extension
15
8
7
0
Example
R7 is loaded with the Timer/Counter value. The operation of the sign-extend
instruction expands bit 8 to bit 15 with the value of bit 7.
R7 is then added to R6.
MOV.B
&TCDAT,R7
; TCDAT = 080h:
. . . . . . . . 1000 0000
SXT
R7
; R7 = 0FF80h:
1111 1111 1000 0000
ADD
R7,R6
; add value of EDE to 16-bit ACCU