[Mark1960]

I was wondering if you had considered, as the 6402 does not require software initialisation, it could be set up with fairly simple hardware to bootstrap the processor on a ram only system.

Either by setting up the processor to read from the 6402 instead of memory, until a flag is set, then send it instructions to write to memory.

Or write all data received by the 6402 to memory and force nops on the processor to increment the address, but this might need a fixed data length counter.

Both of the above would use the 6402 rx data ready to hold the processor on each fetch until the data is available.

This would be a more retro version of my system of using an ft245 on a z80.