cmpm.md

CMPM - Compare memory with memory

Operation

[destination] - [source]

Syntax

CMPM (Ay)+,(Ax)+

Attributes

Size byte, word, longword

Sample syntax

CMPM.B (A3)+,(A4)+

Description

Subtract the source operand from the destination operand and set the condition codes accordingly. The destination is not modified by this instruction. The only permitted addressing mode is address register indirect with post-incrementing for both source and destination operands.

Application

Used to compare the contents of two blocks of memory. For example:

*   Compare two blocks of memory for equality
    LEA    Source,A0      ;A0 points to source block
    LEA    Destination,A1 ;A1 points to destination block
    MOVE.W #Count-1,D0    ;Compare Count words
RPT CMPM.W (A0)+,(A1)+    ;Compare pair of words
    DBNE   D0,RPT         ;Repeat until all done
    .
    .

Condition codes

X	N	Z	V	C
-	*	*	*	*

From MOTOROLA M68000 FAMILY Programmer's reference manual. Copyright 1992 by Motorola Inc./NXP. Adapted with permission.