[Coco] ?PEEK(&HFF90) RETURNS 126 ON MY UNUPGRADED 26-3124?

[coco at yourdvd.net]

got the gal replacement for the pal. it was squished by the post office
- looked like they stepped on the sucker, but i straightened all those
pins out plugged 'er in and voila - coco 3 mpi :-)
While I had the 3024 MPI opened, I noticed just how different it is from
the 3124. The 3024 should be easy to build an exact clone but using your
gal instaed of the tandy pal - all other circuits at first glance appear
to be standard ttl and some power supply stuff. i made one some time ago
using 74ls138's and 74ls374 latches, etc. to clone the mpi - a lot of
discrete circuitry. had 8 slots, but otherwise worked like a coco 3
mpi. I had planned to replace the 138's with 154's and make 16 slots
(major overkill), but then i popped by paul bartons site and he
mentions the upper bit of both nybbles being used as an enable disable
of the associated signal. I didn't think the multi-pak worked like that
and didn't account for it in the thing i built, but it still worked :-)
one day i'll dig all this junk i made out of storage and stick the
schematics somewhere.... r

p.s. i made the slots out of a short piece of ribbon cable and a 40 conn
ids connector. 

> -------- Original Message --------
> Subject: Re: [Coco] ?PEEK(&HFF90) RETURNS 126 ON MY UNUPGRADED 26-3124?
> From: Mark Marlette <mark at cloud9tech.com>
> Date: Tue, April 24, 2007 10:57 am
> To: Robert Gault <robert.gault at worldnet.att.net>
> Cc: coco at maltedmedia.com
> 
> Robert,
> 
> I don't have the data right in front of me....hold on let me check  
> C-9's CVS for the mpak manual...
> 
> Nope...have to add it...
> 
> I looked at my source to the .abl code for the GAL, 26-3024 update.
> 
> The new range of the MPI is $FF40-$FF7F.
> 
> If I looked at the 3124 mod that I have already documented at home I  
> could quickly figure out what it's original range was. From my web  
> page it appears that the MPIs unmodified range went into the GIME's  
> address space($ff90).
> 
> The peek makes sure that it is not. This si the first I have heard  
> that it isn't working.
> 
> Done this MANY years ago so I don't recall.
> 
> Sorry for the slow response. Was gone over the weekend and have many  
> business/list emails to reply to.
> 
> Regards,
> 
> Mark
> 
> 
> Mark Marlette wrote:
> 
> 
> Robert,
> What GIME is in your CoCo?
> Test performed on the same CoCo?
> I'm sure I have done this test on both MPIs. Been too long ago.
> Thanks,
> Mark
> At 4/21/2007 02:12 PM, you wrote:
> 
> 
> Marks test of ?peek(&hff90) returns 255 on all of my 3024 multi-paks,
> however it returned 126 on my 3124. I opened the 3124 and there is no
> satellite board nor any piggy backed chips nor any mod of any kind - i
> can't see that this pak has been upgraded. Does this test only work for
> the 3024's? thanks - Rob
> 
> 
> I just tried a test with a Coco3 and an MPI 3024. Without the MPI the  
> PEEK returned 126 and the same with the MPI.
> 
> What are you trying to determine with this PEEK, whether the MPI was  
> upgraded for Coco3 use?
> 
> 
> 
> 
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