Texas Instruments MSP430x1xx User Manual page 106

Instruction Set
* TST[.W] Test destination
* TST.B Test destination
Syntax TST
TST.B
Operation dst + 0FFFFh + 1
dst + 0FFh + 1
Emulation CMP
CMP.B
Description The destination operand is compared with zero. The status bits are set accord-
ing to the result. The destination is not affected.
Status Bits N: Set if destination is negative, reset if positive
Z: Set if destination contains zero, reset otherwise
C: Set
V: Reset
Mode Bits OSCOFF, CPUOFF, and GIE are not affected.
Example R7 is tested. If it is negative, continue at R7NEG; if it is positive but not zero,
continue at R7POS.
R7POS
R7NEG
R7ZERO
Example The low byte of R7 is tested. If it is negative, continue at R7NEG; if it is positive
but not zero, continue at R7POS.
R7POS
R7NEG
R7ZERO
RISC 16−Bit CPU
3-70
dst or TST.W dst
dst
#0,dst
#0,dst
TST R7 ; Test R7
JN R7NEG ; R7 is negative
JZ R7ZERO ; R7 is zero
...... ; R7 is positive but not zero
...... ; R7 is negative
...... ; R7 is zero
TST.B R7 ; Test low byte of R7
JN R7NEG ; Low byte of R7 is negative
JZ R7ZERO ; Low byte of R7 is zero
...... ; Low byte of R7 is positive but not zero
..... ; Low byte of R7 is negative
...... ; Low byte of R7 is zero