> Question for experienced 16C84 assembler programmers:
> In your experience, what is the most severe limit on a 16C84:
> - processing speed
> - stack depth
> - code size
> - data size (file registers)
> - eeprom size
> - I/O pins
> - ????

Well, almost any design can trade off some of the above for others or for
external circuitry.  For example, the lack of I/O may be mitigated by the
addition of one or more 74HC595 (serial->parallel) or 74HC165 (parallel->
serial) chips.  Using 3 pins, you can add any number of outputs or inputs
(each 595 or 165 will get you 8 more).  Use 4 pins and you can add any
number of outputs AND inputs.  The only limitation is that you must shift
out ALL of the bits in order to read or write any (note that the 595 is
double-buffered, so the outputs will be glitch-free while shifting data).

I have never found the stack depth on the '84 to be a problem; I'd say the
most common limitation I've hit (on the 'C84) was a lack of registers; the
double-size register file on the 'F84 should make that less of a problem.
Otherwise, I've run up against all the other limitations but fount the most
common obstacle to using an '84 is simply price; it costs more than the other
OTP devices.  Otherwise I just love the things.