Texas Instruments MSP430x1xx manual Tst.B

Instruction Set

* TST[.W]	Test destination
* TST.B	Test destination
Syntax	TST		dst or	TST.W dst
	TST.B		dst
Operation	dst + 0FFFFh + 1
	dst + 0FFh + 1
Emulation	CMP		#0,dst
	CMP.B		#0,dst
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.
			TST	R7	; Test R7
			JN	R7NEG	; R7 is negative
			JZ	R7ZERO	; R7 is zero
	R7POS		......		; R7 is positive but not zero
	R7NEG		......		; R7 is negative
	R7ZERO		......		; R7 is zero
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.
			TST.B	R7	; Test low byte of R7
			JN	R7NEG	; Low byte of R7 is negative
			JZ	R7ZERO	; Low byte of R7 is zero
	R7POS		......		; Low byte of R7 is positive but not zero
	R7NEG		.....		; Low byte of R7 is negative
	R7ZERO		......		; Low byte of R7 is zero

3-70 RISC 16−Bit CPU