Re: A82: Return from interupt

To: Assembly 82 list <assembly-82@lists.ticalc.org>
Subject: Re: A82: Return from interupt
From: Eric Piel <pieleric@etu.utc.fr>
Date: Sat, 7 Aug 1999 00:37:13 +0200 (MET DST)
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Delivered-To: assembly-82@lists.ticalc.org
In-Reply-To: <Pine.OSF.3.96.990806090540.27477A-100000@cassius.its.unimelb.edu.au>
Reply-To: assembly-82@lists.ticalc.org


Thank you very much
I had also noticed about the port 03 but I saw in the port82.txt that bits 2-0
where unknown which let me think it couldn't be that !
Thank
Eric

On Fri, 6 Aug 1999, Jeremy Wazny wrote:
 
> 
> 
> I encountered the same problem with the greyscale interrupt. When I looked
> at the code around $0038 (as far as I can remember) I noticed port 3 was
> being written to for some reason. I can't recall at the moment why, but
> the following code seems to work well enough if you plan to exit with an
> ei /reti combo:
> 
>  xor a                  ;Not sure about this value, but seems to work
>  out ($3),a             ;also unsure about why the first out is necessary
>  ld a,%00000010                  
>  out ($3),a
>  ex af,af'              
>  exx
>  ei                     ;enable ints
>  reti                   
> 
> I'm not sure why the first out is necessary, but the calc would crash
> without it. I'm pretty sure Dines' 82port document says something about
> bit1 when writing to port3, but I don't have it to look at at the moment.
> As for the emulators, I don't know of any which actually simulate the
> ports on the 82 properly.
> -Jeremy

References:

Re: A82: Return from interupt

From: Jeremy Wazny <j.wazny@ugrad.unimelb.edu.au>