Gate-level schematics of 6502?

[halkun]

Does there exist a gate-level schematic diagram of the 6502? I was thinking about simulating it in a logic gate simulator, and the most I have found is a block diagram (that I've read may be inaccurate)

I would like to use the 6502 for a class on beginner chip architecture. (Kind of like how C. elegans is used as a model organism for biology)

Pointing me in a good direction would be helpful.

[BigEd]

That's a nice idea!

I don't believe a gate-level schematic does exist, although I think at least one gate-level model has been built. There are just a couple of circuit features which need to be finessed, namely the bidirectional pass gates joining the busses, which are not readily handled by normal logic simulation.

It would take a little searching to come with concrete references to help you - maybe later, but I can't do it now.

[Dr Jefyll]

Ed is the search wizard. But on my HDD I have a couple of files that seem close to what you're looking for. Edit: Unfortunately it's unclear whether I have permission to re-distribute them. I have a feeling Ed will follow up on this.

[BigEd]

I'm going to follow the old dictum that it takes more effort to write something short, so here's a bit of a dump of relevant threads - you'll find pointers to the visual6502 project which should be useful. That project contains the definitive and complete transistor-level description of the 6502, but not in a format that's immediately digestible for other purposes. You will have to roll up your sleeves!

Recently Andrew Holme did some work which is perhaps a very good starting point:
http://www.aholme.co.uk/6502/Main.htm

Check the wiki at visual6502.org - search for hanson, for schematics, and for balazs.

You will find Donald Hanson has got enormous copies of original schematics for the 6502, and has had them scanned, but has not yet published them. Some people do have copies, and there are excerpts on the wiki. These schematics are a mix of transistor level and logic gate level - I would say they are of great historical interest but limited practical use.

Relevant threads about gate-level reconstructions and about the innards of the 6502:
A couple assorted questions about internal structure of 6502
visual6502: Help me understand this internal bus of the 6502
Two transistors' Output In One Node
Breaking 6502 apart

New Verilog 6502 core
The MOnSter 6502 - a transistor-level recreation on one PCB.
TTL 6502 Here I come
visual6502 Q: Trying to understand every transistor.
Logisim & cpu's
Visualizing the 6502

[halkun]

Wow! You guys are quick! I'll digest this later when I get home. I just came across the Logisim bi-directional bus problem. I may get away with doing things on the block level and some creative bus management.

In course I'm writing, I was thinking of gluing together a bunch generic 74xx chips (using a 74181 ALU) to make a simple simulated CPU, but the idea of using a rather famous little chip is a little more enticing.

[BigEd]

Just for fun, here's Dr Donald Hanson with the two sheets (datapath on the left, PLA and random logic on the right):

[joelnoche]

See the "6502 svg schematic" topic in this forum: viewtopic.php?t=6053

[org]

Try this: viewtopic.php?f=8&t=6903

[joelnoche]

org wrote:

Try this: viewtopic.php?f=8&t=6903

Wow. Thanks for this!