Peter Keller wrote:

> I did not track the whole conversation. So, what original part are you
> going to replace?

  He mentioned the 6803, which is a ROM-less version of the 6801.  This
is the predecessor to the 68HC11, and like it, has code halfway between
6802 (6800) and 6809.  It also has some I/O on-board which is however
mostly "nobbled" by using 18 port lines for external bus access, and
includes a timer and UART.  A 6801 is equivalent, the ROM being
bypassed.

  6802 (6800) or 6809 chips probably wouldn't be useful as other
interface chips would need to be added.  Code-wise, the most direct
move would be to a 68HC11 though some modifications of timer and UART
code would be necessary for starters.

  Swapping for a PIC would certainly be one possibility, or
supercharging it with an Atmel AVR!
--
  Cheers,
        Paul B.