[Coco] [Color Computer] Re: Coco flash cartridge
msmcdoug at iinet.net.au
Tue Sep 25 02:04:31 EDT 2007
James Diffendaffer wrote:
> That's ok for a prototype but for production you have to remember that
> most people would want to reuse a game cart case if it will fit. That
> probably means some sort of right angle switch or solder pads to
> attach a remote switch. And if you plug it into a multipak interface
> you would have to feel around for the button even if the board isn't
> in a case if you use that button.
Yeah, this is really just a prototype, because if it went into production,
the tooling costs would have to be re-done for a panel anyway. I only have
one Coco cart atm - DoD - and I'm not about to rip _that_ apart! ;)
> I suppose you might be able to have a timer in your PLD
> as an alternative.
If there's enough register bits left for a long enough timer, then sure!
> LOL... don't you just hate scope creep?
And it's worst when you're spec'ing your own design! ;)
>>> I'd like to develop some stuff for the board, let me know how much >>it
>>> will cost for one. If you can provide the info on the ports ahead
>>> of time that would be nice.
I did my BOM at lunchtime today. Farnell want $15 for a 4MB flash. I haven't
tried sourcing it anywhere else yet.. the other parts are almost
negligible... the CPLD should cost a few dollars IIRC...
> Read only is fine... we'll just have to track the page in software.
Unfortunately, D2 & D3 are wired to input-only pins on the CPLD. I
originally had RESET# & CART# wired to them, and didn't realise until I had
almost finished the layout. It was too difficult to wire any of the address
lines to those pins, so D2&3 it was. I didn't think there'd be a real need
to read the bank as it is not unusual to have shadow registers in software
anyway. Alternatively I could always make it readable via the 2 high nibbles
of address 0 & 1 if need be. In most cases it'll only be paging small ranges
so it may only need the LS bits anyway....
> Sounds fine to me but I haven't programmed flash chips directly in
> years and back then you even needed to manually erase them.
These parts erase in 64KB pages - at least the 4MB one does. Programming is
done by writing a 'magic sequence' to certain addresses and IIRC you can't
read whilst erasing (I'd have to check) but you simply need to poll the
RDY/BSY# bit until it's done.
> You have to be able to reset until artifact colors are correct without
> resetting the bank but you must be able to reset the bank without
> turning the machine off. And since the system will probably die in a
> horrible manner if you reset the bank you are better off just
> resetting the system along with it.
Thanks for the feedback!
| Mark McDougall | "Electrical Engineers do it
| <http://members.iinet.net.au/~msmcdoug> | with less resistance!"
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