6502 Development & Fiddler-Board

[ShakingMyToe]

Hello everyone,

I've been learning to programm the 6502 on my computer for some time now.
I've always loved the CPU, and now I would really like to get started with the hardware.
For that, I was hoping I could build a board that would include everything I would need to test things out in reallife.

One of those things would be something to control VGA output to a small monitor, for example.
Or adding a PS/2 compatible-communication-board to allow for changes made by the user.

It could be much more simple, but I would really like to take a soldering iron in my hand and get on-hand-experience with the hardware-side of things.
So with that said, I would much appreciate it if you could help me find the resources that I need to get started.

I've seen this guy make a computer out of the 6502, something similar to this would be amazing, but more documentation on the process and how it works would be even better:
https://www.youtube.com/watch?v=SDTCEztQZsI

Many thanks in advance!

[GARTHWILSON]

See my 6502 primer, at http://wilsonminesco.com/6502primer/ .

[ShakingMyToe]

GARTHWILSON wrote:

See my 6502 primer, at http://wilsonminesco.com/6502primer/ .

Hey, thanks for the reply!
It's looking great so far. Do you think the documentation will help me even with a newer 64c02? I can tell that the clock generation deviates a bit, as:

Quote:

NOTE about the next two circuits: WDC no longer tests or specifies the gate delays between Φ0 in, Φ1 out, and Φ2 out for their newer 65c02's, and they would prefer that the designer use an external oscillator. All the same internal inverters seem to still be in place however, so I have little doubt that the circuits below will still work fine; but I had to pass the info on.

[GARTHWILSON]

There have been a lot of small problems in WDC's data sheets. Another recent topic here is covering those. Fortunately the actual parts are always better than the data sheets let on, except for a notorious bug in the W65C51S where the transmit-register-empty bit in the status register is stuck in the "on" position (it worked in simulation before the silicon was made, but a difference in the faster silicon process caused a race condition which resulted in the problem), and there's a bug in one of the shift-register modes in all 65(c)22's which is of no consequence for most users.

The 6502 primer is for making your own '02 computer though, and when you're building a new one, it only makes sense to use the superior CMOS part, not NMOS. I really wish the NMOS would just go away (so does Bill Mensch), except that there are people writing software for others with vintage computers who won't be changing the processor, or who can't, like for the Commodore 64 which used the 6510 which was never available in CMOS. The C64 and other computers of its day have a huge place in computer history.

As for the quoted note, it's just that. If you want to go with that, it would be easy to make the slight modification in the design to connect an external clock source's output to Φ2 for the entire circuit as well as pin 37, and then leave pin 39 open. In spite of the note, I have no doubt that the circuit will work either way. I've been using a WDC W65C802 for many years the old way, and it has never had a problem, even overclocked.

[Alarm Siren]

GARTHWILSON wrote:

it worked in simulation before the silicon was made, but a difference in the faster silicon process caused a race condition which resulted in the problem

Citation?

Also, I know its repeating what everyone already knows, but I still can't believe they havn't fixed that bug after 4 years or however long its been. That's not a minor defect like the one in the VIA, that fundamentally breaks core functionality of the chip. As soon as it was discovered the lot of them should have been recalled.

[GARTHWILSON]

Alarm Siren wrote:

GARTHWILSON wrote:

it worked in simulation before the silicon was made, but a difference in the faster silicon process caused a race condition which resulted in the problem

Citation?

Bill Mensch told me personally in a conversation.

[Alarm Siren]

fair 'nuf

[BigEd]

Hold time violations... they can get you every time. These days we use static timing analysis as the backstop, because simulation can only catch so much. I wonder if WDC had the tools.

[EugeneNine]

Makes one wonder what other race conditions there might be. Scary to think when they are using in medical equipment.

[GARTHWILSON]

The '51 is the only one that has only recently been brought up to 14MHz speeds. The others have been there for 20+ years without showing any problems, except the old shift-register mode-011 bug in the '22 as mentioned earlier. I think this is also the first time WDC has made the '51.

[BigDumbDinosaur]

EugeneNine wrote:

Makes one wonder what other race conditions there might be. Scary to think when they are using in medical equipment.

To my knowledge, the W65C22 and W65C51 have never been certified for use in medical devices.