[Coco] Cartridge memory - mapping in and out

[Mark McDougall]

Mike Pepe wrote:

> If this were my project, I'd use an "indirect" method to program the 
> flash. I'm thinking something like Tony D.'s ubiquitous auto-increment 
> circuit he uses in his super floppy controller, ram disk, and eprom 
> programmer. You can use a few addresses in the *SCS range to program the 
> flash.

This whole project only came about in the 1st place because I noticed people 
talking about EPROM carts on this mailing list and we had spare space on a 
panel that had been sitting there for 6 months waiting to be sent out.

My 1st idea was a 'proto' cart, but then I scaled it back to a simple EPROM 
cart. Whilst designing that I thought it would be a simple matter to add 
flash and have it programmed from the Coco. I put the design out there for 
comments, but ultimately I'm guilty of not doing the research myself.

My 2nd incarnation (Coco Flash2) uses a CPLD, but falls short of decoding 
all the address lines due to the low pin count. Fortunately, I *think* I 
have a solution - one that won't risk the cart or coco at all, and doesn't 
rely on manual switching by the user. I'm currently waiting on CPLDs...

Had the CTS# line been driven during a write cycle, then in theory my 
designs should have been sufficient. I must admit that I did wonder about 
write cycles mapped to ROM, but (rather foolishly) ignored the question. 
Well at least I learnt something...

Regards,

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