Re: A83: CP with register DE?

To: assembly-83@lists.ticalc.org
Subject: Re: A83: CP with register DE?
From: Dsc984@aol.com
Date: Fri, 29 Jan 1999 11:38:44 EST
Delivered-To: assembly-83-outgoing@towerguard.unix.edu.sollentuna.se
Delivered-To: assembly-83@lists.ticalc.org
Reply-To: assembly-83@lists.ticalc.org


In a message dated 29-01-99 11:07:30 AM Eastern Standard Time, AtmaZ@aol.com
writes:

<< Hi all,
 
 What the sources on Z80 ASM have taught me is that CP only works with
register
 A.  However, the below usage of CP is contradictory to that rule...take a
look
 at this.
 
 Here's the code:
 
 call _getk         ; get keycode
 call _op2toop1  ; swap OPs
 call _convop1     ; put OP1 in -->DE<-- and not A
 cp  22 		     ; compare with [MODE] keycode
 ret   z              ; exit if pressed
  >>

This works because CP compairs to a, not with a.  So, when you do cp 22, it
checks to see if a=22.
-David

Prev: A83: contrast
Next: Re: A83: contrast
Index(es):
- Main
- Thread