[Coco] MPI writing to $c000

[RETRO Innovations]

On 1/24/2016 11:15 AM, Darren A wrote:
> On Sun, Jan 24, 2016 at 9:14 AM, RETRO Innovations wrote:
>
>> On 1/24/2016 8:44 AM, Robert Gault wrote:
>>
>>> I doubt I can help with your PAK but the obvious issue that comes to mind
>>> is whether you have set the MPI data at $FF7F correctly so that your
>>> external ROM/RAM has access. After all, your device works when directly
>>> connected to a Coco. :)
>>>
>> I hav put a scope on the WE line, and I am seeing the trigger, so I
>> believe the correct slot is selected.
>>
>>> The high nibble at $FF7F selects the MPI slot for RAM/ROM. The low nibble
>>> selects the slot I/O at $FF40-$FF5F.
>>>
>>> Perhaps you meant that even with the MPI set to the correct slot for your
>>> cart the RAM is not working. If that is the case, are you having failures
>>> with any other cart that contains a ROM when plugged into the MPI?
>>>
>> All my MPI carts ROMs read fine.
>>
> You may want to check if the address signals (A13 to A15) are making their
> way through the MPI to the cartridge. Most ROM paks and disk controllers do
> not use those address lines, so a connectivity problem with them would not
> normally show up.
>
> - Darren
>
I'll put it all on the LA this week (kinda frustrated right at the 
moment, so my inventive to wire it all up to the LA is low), but the 
scope sees the !WE signal strobing

-- 
RETRO Innovations, Contemporary Gear for Classic Systems
www.go4retro.com
store.go4retro.com