Texas Instruments MSP430x4xx - Manual (Page 103)

Instruction Set
3-69 RISC 16−Bit CPU
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 3−19.
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 3−19. Destination Operand Sign Extension
15 8 7 0
Example R7 is loaded with the P1IN 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 &P1IN,R7 ; P1IN = 080h: . . . . . . . . 1000 0000
SXT R7 ; R7 = 0FF80h: 1111 1111 1000 0000