> > Unless I find more 6303 info, I'll probably be better off using a different processor. Since

Probably similar to the 6301 used in the Epson HX20, for instance. To
go a little further, it's like a slightly cut-down 6809. I think it
supports the dual accumulator instructions, but not the multiply
instructions.

> > More obscure Roland MCU antics Same deal goes for my Juno106! It uses a upd7810
> > processor, but of course I can't find any info on those either. Guess I am out of my
> league

>From the name it sounds like it may be a Z80-derived chip, possibly with

some on-board interfacing.

If you disassemble the ROMs, you can often figure it out. The 6809
series has a table of interrupt and reset vectors at the top of the ROM,
which is intended to sit at the end of the memory map. The Z80 has
"restart" instructions, with little 8-byte slots at the start of the ROM
which is intended to sit at the bottom of the memory map. Generally
these will end with a 3-byte absolute jump to a location in ROM,
particularly the first restart which is the reset handler.

Gordon