Texas Instruments MSP430x1xx - Manual (Page 372)

Instruction Set Overview
B-22
CMP[.W] Compare source and destination
CMP.B Compare source and destination
Syntax CMP src,dst or CMP.W src,dst
CMP.B src,dst
Operation dst + .NOT.src + 1
or
(dst – src)
Description The source operand is subtracted from the destination operand. This is
accomplished by adding the 1s complement of the source operand plus 1. The
two operands are not affected and the result is not stored; only the status bits
are affected.
Status Bits N: Set if result is negative, reset if positive (src >= dst)
Z: Set if result is zero, reset otherwise (src = dst)
C: Set if there is a carry from the MSB of the result, reset otherwise
V: Set if an arithmetic overflow occurs, otherwise reset
Mode Bits OscOff, CPUOff, and GIE are not affected.
Example R5 and R6 are compared. If they are equal, the program continues at the label
EQUAL.
CMP R5,R6 ; R5 = R6?
JEQ EQUAL ; YES, JUMP
Example Two RAM blocks are compared. If they are not equal, the program branches
to the label ERROR.
MOV #NUM,R5 ; number of words to be compared
L$1 CMP &BLOCK1,&BLOCK2 ; Are Words equal?
JNZ ERROR ; No, branch to ERROR
DEC R5 ; Are all words compared?
JNZ L$1 ; No, another compare
Example The RAM bytes addressed by EDE and TONI are compared. If they are equal,
the program continues at the label EQUAL.
CMP.B EDE,TONI ; MEM(EDE) = MEM(TONI)?
JEQ EQUAL ; YES, JUMP
Example Check two keys connected to port pins P0 and P1. If key1 is pressed, the pro-
gram branches to label MENU1; if key2 is pressed, the program branches to
MENU2.
P0IN .EQU 010h
KEY1 .EQU 01h
KEY2 .EQU 02h
CMP.B #KEY1,&P0IN
JEQ
MENU1
CMP.B #KEY2,&P0IN
JEQ
MENU2