[Coco] [Color Computer] Cartridge memory - mapping in and out

[Mark McDougall]

Mark McDougall wrote:

> My colleague had an idea... put the cart into a special mode where the 
> *next* write also writes to the flash... since the flash will be 
> programmed in 16/32KB pages, the shadow writes will go to the bottom of 
> RAM... of course this would need to be done (carefully) in ML...

Interesting, I might be able to salvage CocoFlash... if I connect RW# to 
CTS# via a DIPSWITCH, then I can do as follows...

1. ML program starts up and disables interrupts. Prompts user to switch to 
"program mode" on DIPSWITCH
2. With careful use of memory variables and stack, all WRITES will be 
honoured on the flash chip, because CTS# is driven by RW#. Since there's 
only a 16/32KB window, I can even write to the lower 16/32KB of coco space 
to program the flash. Fortunately the chip I'm using has a 0 setup on CS# 
and 0 data hold time. Using byte programming mode, I could even use memory 
variables in the programming routine, as invalid writes will be ignored - 
even if I need to write the reset sequence on every byte.
3. When done, prompt the user to disable "program mode".

Any holes in this?

Regards,

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