Compare two Address Registers in Motorolla 68k

Question

I have a simple program, where I'm trying to understand how to compare two address registers, and branch if A1 is less than or equal to A2

As such:

    ORG    $8000
START:                  ; first instruction of program

    CMP A2,A1
    BLE LOOP ;if A1 is less then or equal to A2, BRANCH

LOOP: 

* Put variables and constants here

    END    START        ; last line of source

Is this the correct way of doing it? What if I used the macro CMPAhere instead, would it make a difference?

Answer 1

You have to use cmpa to compare with an addressregister on 68K. You don't have a choice.

Also it's best to include the size suffix .L to make sure the full 32 bits are compared as opposed to a sign-extended version of the low 16 bits.

CMPA.L A2,A1
BLE.S  LOOP