Datasheet

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Instruction Set

3.4.6.14 CMP

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

(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

MOV #BLOCK1,R6 ; BLOCK1 start address in R6

MOV #BLOCK2,R7 ; BLOCK2 start address in R7

L$1 CMP @R6+,0(R7) ; Are Words equal? R6 increments

JNZ ERROR ; No, branch to ERROR

INCD R7 ; Increment R7 pointer

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

SLAU144J–December 2004–Revised July 2013 CPU

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