[Coco] GIME questions

[David Gacke]

Hi Robert,

Here's the setup I've got. I've got a daughterboard I made jammed into
the 6809 socket of my CoCo 3. Then I have a ribbon cable back to my
dsPIC demo board with a 30F6014 on it.

Connected to that, I have a Microchip ICD2 pod for downloading new code
into the microcontroller.

The CoCo 3 itself is a stock model with 512K of RAM.

But from what you're saying, maybe I have a high order address line
hosed up or something.  I'll double check those again with the scope to
verify.

Who knows. Maybe I've just got bit addr15 and addr14 shorted or
something goofy.


Thanks for your help.

Dave 

-----Original Message-----
From: coco-bounces at maltedmedia.com [mailto:coco-bounces at maltedmedia.com]
On Behalf Of Robert Gault
Sent: Monday, August 16, 2004 12:23 PM
To: CoCoList for Color Computer Enthusiasts
Subject: Re: [Coco] GIME questions

David Gacke wrote:
> 
> 
>>Actually that is not the case. The code from Begmove ($C03F) through 
>>Endmove ($C36C) is copied.
> 
> 
> Right, this is what I "should" see, but I'm guessing I've got the GIME
> misconfigured somehow.
> 
> I know I'm seeing the ROM at $4000 as well because when I try and
write
> over it, it doesn't care. The values don't change.
> 
> 
> I'm just not quite sure how to configure the GIME to do this
> intentionally.  What I was hoping for was an answer of:
> 
> 
> Here, jam this X value into FF90, and these X values into FFAx, then
jam
> this other value into FF90 and you'll see the scenario you're talking
> about....
> 
> 
> Since we're on the GIME, can you modify the FFAx registers while the
MMU
> is enabled?
> 
> Anyway, thanks very much for the advice. It's good to have a list
where
> someone will tell me how I'm wrong when I actually need it!  :)
> 
> 
> 
> Dave
> 
> 

I'm not sure if you can move the ROM's to the $4000 location in memory. 
If it is possible, you would need to set either $FFA2 or $FFAA to $3E to

make $C000-$DFFF echo there. Problem is there is no switch to convert 
$0-$7FFF to ROM.

If you really are seeing ROM's at $0-$7FFF, you are not emulating the 
GIME correctly. There is also no method in the specs for making a SAM 
MC6883 put ROM in the lower half of memory.


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