Hi guys

It's been a while since I last posted regarding my first 6502 project. I previously managed to breadboard and then do a soldered design for a simple 65C02S CPU, 32K SRAM, 32K ROM, and 65C22S VIA setup. Unfortunately, I ran into bus stability issues -especially when interfacing with the VIA- with the soldered version. Despite a lot of helpful advice from here and me spending a lot of time trying to diagnose the PCB, I couldn't get the wretched thing to behave.

I've now finished the wirewrap version ... and it works! I can reliably write to and read back from RAM, run instructions and set the VIA port A to output a bit pattern.

Here are a few pics (see below).
Many thanks to all the guys who helped me months back with advice and also for the excellent documentation on this website/these forums

BTW the extra PCB with the LEDs on it is a (very crude!) bus monitor outputting A0-15, D0-7, /RAM select, /ROM select, /VIA select. All LEDs are current limited to draw 1-2mA each

Here's the very basic test code I used first for testing RAM and then for VIA:

RAM check



65C22S VIA test (port A output):

Here's the circuit diagram

Just in case anyone is interested here's the assembler output:

Congrats! It always feels good to have one work as planned. What's next?

Daryl

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Please visit my website -> https://sbc.rictor.org/

Congratulations! And thank you for the circuit diagram, it's always great to be able to look at another working example ...

Was this your first time wire-wrapping? Anything you can recommend to those who are about to start to learn how?

Answering Wire-Wrap (WW) Questions and Doubts:
http://wilsonminesco.com/6502primer/WireWrap.html

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

@8BIT
Cheers . I think the next stage is to get some form of input and output sorted. possibly an LCD display and a basic keyboard. Otherwise I won't have much to muck around with

@SCOTWS
No worries and thanks . It was indeed my first try which is why I'm a bit surprised (in a good way!) that it worked so well.
Regarding recommendations: The wire wrap stuff was surprisingly easy once I got the hang of it with only the odd botched one. Garth's guide (http://wilsonminesco.com/6502primer/WireWrap.html) was invaluable - especially with regard to the type of wire wrap tool to buy (I got mine off of ebay for roughly £40 - don't skimp on this if you can avoid it).
Testing wise, I got a small piece of perf board, put in a wire wrap DIL socket on it, anchored it with a bit of bluetak and practiced on that. Most of it is not forcing the wire wrap tool, but simply gently turning the tool at a slow but consistent rate and without pressing down so that the wire layers on top of itself vertically. If you try to force it then it all goes wrong plus you also can't feel it going wrong either (which you can if you're doing it correctly). I recommend doing a comparrison of any test ones you do against the pictures that Garth has in his Q&A guide.