Re: A83: Out of Range.

To: assembly-83@lists.ticalc.org
Subject: Re: A83: Out of Range.
From: ComAsYuAre@aol.com
Date: Mon, 7 Feb 2000 14:38:02 EST
Reply-To: assembly-83@lists.ticalc.org


In a message dated 2/7/00 2:29:59 PM Eastern Standard Time, david@acz.org 
writes:

> No, they do.  He was explaining how they would be used to store jump
>  addresses.
>  
>  A byte is only enough to hold a relative address.  A word is enough to 
store
>  an absolute address.
>  
>  However, doing a '.db exit' will NOT store the relative address.  Relative
>  to what?  There is no way for the assembler to tell.  It will attempt to
>  store the absolute address and give a warning (at least it should!) that
>  there is unused data.  If you really need to store a relative address, it
>  can be done as follows:
>  
>  Label =$+1
>   jr 0
>  
>   .db Exit-Label

Actually that would be one byte off because it offsets from the start of the 
opcode.  You'd need to do it like this:

 ld a,(address)
 ld (label+1),a
label:
 jr 0


address:
.db exit-label

>  
>  In this case, the relative address will be used for the JR below 'Label'.
>  
>  > > db exit = Relative address of exit (like jr)
>  > > dw exit = Absolute address of exit (like jp... or ld (...),...)
>  >
>  > So 'db' and 'dw' have nothing to do with 'data byte' and 'data word'?
>  
>  



----
Jonah Cohen
<ComAsYuAre@aol.com>
http://linux.hypnotic.org/~jonah/

Follow-Ups:

Re: A83: Out of Range.

From: "David Phillips" <david@acz.org>