[Coco] 256K SuperROMPak (32 Banks)

[RETRO Innovations]

So, what are the options to map RAM into the address space from the cart 
port?  That is the key, right?

I admit my signal understanding is weak, but I would assume SLENB would 
do it, so you could do:

map a latch into IO space on the cart.
Have one of the bits of the latch drag SLENB active (via some logic that 
only makes SLENB go active on writes on some address range (0000-7fff?)
Then, any writes to some address range would trigger SLENB, which would 
map the FLASH into the address space.  Hitting the latch again would 
move the FLASH out of the write space.

Someone is going to shoot me design down, but surely something like that 
would work.

It can't be tougher than writing data on the C64.  To do flash 
programming, one must place the machine in Ultimax mode, which maps out 
all RAM/ROM except a small 4K chunk at $0 and the ROM at $e000, as I recall.

JIm