[Coco] [Color Computer] Coco flash cartridge

[Mark McDougall]

James Diffendaffer wrote:

> Mark, if you remove the dipswitch and add a latch that can be written
> to on the computer the flash cart can be used as a multicart with a
> menu to select the game you want to play.  This has been done on the
> Atari's, Vectrex and several other systems.

Heh, I originally intended a CPLD-based 'proto cart' after reading threads 
on this mailing list, but when that proved too ambitious for a 2-layer 
project I scaled it back to a quick 'n' dirty one-afternoon job... now with 
feature-creep it's tending back towards the original project ! ;)

Now, I can see a problem is decode - whatever address range is used to 
address the latch (eg SCS#) won't be able to be written to the flash... I'm 
wondering if that will cause problems with some carts on the coco3?

The other issue I can see a problem with is auto-start. With latch-enable 
tied to, say SCS# and RW# and output-enable tied active, is the power-up 
state of the latch deterministic? If not, then say goodbyte to auto-start... 
otherwise if it is, I guess you could use one latch output for the 
auto-start control, and set it after power-up via software so subsequent 
hard-resets ran the selected image...

Hmmm... more logic, more routing... not sure if I have time to implement 
this on the current board... would be nice but might have to wait for the 
more fully-featured CPLD cart...

Regards,

-- 
|              Mark McDougall                | "Electrical Engineers do it
|  <http://members.iinet.net.au/~msmcdoug>   |   with less resistance!"