I am looking for a transistor-level schematic for the 65C02, something like the one for the 6502 created by davidmjc (https://github.com/davidmjc/6502).

I am a teacher planning to give a student project to implement the 6502 using Digital software (https://github.com/hneemann/Digital). But the schematic of davidmjc has depletion-mode MOSFETs which the Digital software does not have. So I'm hoping that the transistor-level schematic of the 65C02 uses only enhancement-mode MOSFETs.

Do you know of any source for a 65C02 transistor-level schematic (or at least a very detailed circuit diagram)?

  • 1
    According to wikipedia, WDC still makes the W65C02S-14, so I guess a openly available schematic would run into intellectual property issues... why not implement a microprocessor design with no IP issues?
    – dirkt
    Mar 14, 2022 at 12:55
  • @dirkt, thanks. That's probably why I couldn't find a 65C02 schematic. But I'd like to keep this question open for a while to see what others have to say.
    – JRN
    Mar 14, 2022 at 13:10
  • 3
    The last time I was involved with the WDC 65C02 the IP (i.e. schematic and IC layout) was available only to licensees. I doubt that has changed. Today WDC offers IP as cores, both a layout version and a Verilog RTL implementation that can be realized using the usual tools. If you want these, you will need to license the IP. I'll note, however, that the 65C02 schematic design is not significantly different from the original NMOS 6502. It might be a good exercise for your students to convert NMOS to CMOS. There is an educational IP license mentioned on the WDC site that you might look at.
    – jwh20
    Mar 14, 2022 at 13:23
  • I was going to suggest that WDC might be somewhat "sympathetic" to your request, if you contact them directly. Just a guess...
    – Brian H
    Mar 14, 2022 at 14:57
  • 3
    @jwh20: Many aspects of the 6502 design appear to be predicated upon the use of NMOS and its ability to form very large "NOR" gates. Given that, I would not expect a CMOS-based chip to be similar unless it can use some tricks to achieve a similar purpose (e.g. have an internal-bus latch that's constructed like a RAM cell with weak high-side feedback, switch it one way on one clock phase, and then on the other clock phase either leave it alone or switch it the other way. The transistors that switch the bus low would have to fight the high-side driver briefly, but only until they make...
    – supercat
    Mar 14, 2022 at 17:03


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