A89: Re: and now a REAL ASM question!

To: <assembly-89@lists.ticalc.org>
Subject: A89: Re: and now a REAL ASM question!
From: "Thayne Miller" <yomaster@inconnect.com>
Date: Wed, 23 Sep 1998 21:14:02 -0600
Delivered-To: assembly-89-outgoing@towerguard.unix.edu.sollentuna.se
Reply-To: assembly-89@lists.ticalc.org


ok, so do you mean that after the "lea" instruction, AO will POINT to the
beginning of the string?  And therefore if I use "move" it will actually
load the first byte of the STRING into A0 rather than the address of the
string?  I kind of understand, but I just wanted to make sure...  so if I
did:

lea  (A0),A1

and A0 was "1000", then A1 would be "1000" rather than the actual WORD at
memory adress 1000?  Or am I completely screwed up?




>
>>     I'm new to 68k asm, and I was looking over the  hello world program.
>>There's a part I don't understand:   ________________     lea
>>string(PC),A0     move.l  A0,-(A7) ________________   anyway, why can't I
>>use this instead? :   _______________     movea.l    string(PC),A0
>>move.l    A0,-(A7) _______________   I don't quite understand what the
>>difference between  "lea" and "move" is.  Can someone please explain  it?
>>btw, when I use the second piece of code, I get garbled letters on the
>>screen...      __
>
>The difference is that movea moves what is at string(pc) into A0, which is
>useful for getting memory into data registers directly.  LEA (load
>effective address) loads the actual address into A0, so that when put on
>the stack, a subroutine can now use it.
>
>

Follow-Ups:

Re: A89: Re: and now a REAL ASM question!

From: Mark Zavislak <felix@megsinet.net>