A83: CP with register DE?

To: assembly-83@lists.ticalc.org
Subject: A83: CP with register DE?
From: AtmaZ@aol.com
Date: Fri, 29 Jan 1999 01:03:47 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


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

And this works, for some strange reason!  I hit MODE and the program exits.
Can anybody tell me _why_ this works?

Chances are that the answer is painfully obvious and I'm just slow, but...hey,
what the hell.

--David

Follow-Ups:

Re: A83: CP with register DE?

From: Linus Akesson <lairfight@softhome.net>

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