(Oops! Lots of activity on this topic just as I finished preparing to post!)
Hi, Michael. Allow me to echo the nudge (so to speak
) toward the '816. Maybe it's hard to believe that this SuperProcessor has a secret identity, and is willing to play the role of a meek, mild-mannered 65C02. But that is the case. Without any action by you, it'll automatically power up in emulation mode and stay there as long as desired -- indefinitely, if need be. As BDD says, the learning curve isn't a prerequisite.
But if DIP-ness and 8-bit-hood are what make you comfortable then I'm willing to donate a Rockwell 'C02 to your cause. Or accept Garth's offer. You are right, BTW, about not being able to stop the clock on an NMOS part. (The RDY input can be used to single-step an NMOS chip without stopping the clock but that's more nuisance than it's worth, IMO. The interrupt technique Garth mentioned is better. Or stick with your plan to actually stop the clock.)
Quote:
I'd like to use a PIC microcontroller to generate the processor clock signal and to load a monitor program into RAM at start up.
How exactly do you plan for the PIC to write to the 65xx's RAM? Are you planning to float (tri-state) the 65xx address bus so the PIC can temporarily assume control of those lines? NB: Rockwell parts have no BE input and thus cannot float the address bus.
FWIW there's an alternative technique, one which doesn't require the 65xx to tri-state the address lines. It drastically reduces both the amount of wiring for the load circuitry and the number of I/O ports lines the PIC will need. Mainly you would need just 8 output bits from the PIC (not 24) plus a few more bits used as strobes. It's something I planned to write up "someday" for 6502.org. Maybe the time has come.
cheers,
Jeff
ps- a brief explanation (and not very beginner-friendly): Need to write, say, EA to address 200? Clock the following bytes onto the data bus one by one: A9 EA 8D 00 02. Some simple preliminary steps cause the CPU to digest this as a two-instruction program:
LDA #$EA then
STA $200. Repeat as required for subsequent bytes to be loaded. A simple hardware hook prevents bus contention.
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In 1988 my 65C02 got six new registers and 44 new full-speed instructions!
https://laughtonelectronics.com/Arcana/ ... mmary.html