Datasheet

Instruction Set Description www.ti.com
4.6.2.49 SXT
SXT Extend sign
SXT dst
Syntax
Operation dst.7 → dst.15:8, dst.7 → dst.19:8 (register mode)
Description
Register mode: the sign of the low byte of the operand is extended into the bits
Rdst.19:8.
Rdst.7 = 0: Rdst.19:8 = 000h afterwards
Rdst.7 = 1: Rdst.19:8 = FFFh afterwards
Other modes: the sign of the low byte of the operand is extended into the high byte.
dst.7 = 0: high byte = 00h afterwards
dst.7 = 1: high byte = FFh afterwards
Status Bits N: Set if result is negative, reset otherwise
Z: Set if result is zero, reset otherwise
C: Set if result is not zero, reset otherwise (C = .not.Z)
V: Reset
Mode Bits OSCOFF, CPUOFF, and GIE are not affected.
Example The signed 8-bit data in EDE (lower 64KB) is sign extended and added to the 16-bit
signed data in R7.
MOV.B &EDE,R5 ; EDE -> R5. 00XXh
SXT R5 ; Sign extend low byte to R5.19:8
ADD R5,R7 ; Add signed 16-bit values
Example The signed 8-bit data in EDE (PC +32 K) is sign extended and added to the 20-bit data
in R7.
MOV.B EDE,R5 ; EDE -> R5. 00XXh
SXT R5 ; Sign extend low byte to R5.19:8
ADDA R5,R7 ; Add signed 20-bit values
212
CPUX SLAU144J–December 2004–Revised July 2013
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