I just wanted to share my little project and a small step stone to my ultimate goal of a 65816 based SBC.

It started as this


A 65C02 at 1Mhz, a 65C51 for serial, a 65C22, two 32k RAMs, and a 128k Flash ROM on bread boards and an unmanageable mess of wires.

It became this


It is basically what I built on the breadboards with a second 65C22 dedicated to bit banging SPI. The design still accommodates the 65C51 which I used to boot strap my SPI code, but now that I have SPI working, I am using a MAX3100 SPI UART instead. I also have a SPI RTC connected, and I am currently working on connecting a PS/2 keyboard with an ATMega328 or 1284 handling the PS/2 protocol and communicating with the SBC through SPI.

And the best thing is I have it running rock solid at 8Mhz! My software SPI implementation seems to have no problem keeping up with a 115200 baud rate on the MAX3100.

Many thanks to Garth Wilson for making his SPI code available which is the basis for my SPI implementation. I added support for SPI mode 0-3 and full duplex communication. If anyone is interested, I will make my SPI implementation available on GitHub or something.

Thanks to everyone who has given me pointers and advice.

Looks great - thanks for sharing! Do please put your code up on github (or similar)

Looks good! I do like the plug-in SPI things too.

Cheers,

-Gordon

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Gordon Henderson.
See my Ruby 6502 and 65816 SBC projects here: https://projects.drogon.net/ruby/

Nice build! I especially like the R/A female headers for ports! What's with the resistor across the pins of the top 6522?

You should put some rubber feet on that beauty so it doesn't fubar your desktop even more than it already has.

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Got a kilobyte lying fallow in your 65xx's memory map? Sprinkle some VTL02C on it and see how it grows on you!

Mike B. (about me) (learning how to github)

The resistor across the 6522 is what happens when you accidentally buy a 65C22N when you meant to get a 65C22S. The 65C22N has a open drain IRQ and the 65C22S does not. The open drain version can have the IRQ line used in a wired OR and needs a pullup resistor. The board was designed for the 65C22S and didn't have the pullup. Bodge a 3K3 resistor from IRQ across to VCC and voila, a 65C22N sorta becomes a 65C22S!

By desk you must mean kitchen table
The wife is still grumpy about that haha.

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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?

Yes, there are more differences than just the open drain IRQ, but that was the difference that got me.
I guess that's what I get for not double checking my order from Mouser

The board was designed so that all of the device IRQs are combined using some 3 input ANDs. The 65C51 also has an open drain IRQ and I did have a pullup on its IRQ with the added benefit that I could remove it when I got my SPI UART going and the pullup would hold that input to the AND gate high. I thought all of my 65C22s were the S version with the totem pole IRQ and did not have any plans for removing them from the board so I did not have pullups for them on the board.

Had lots of fun trying to figure out what was going on with the N version stuck in there.

This is a really nice looking final product.
Great to see it go from breadboard to PCB like that.

Brad

I have my SPI code up on github if anyone is interested.

Here is a link to my post on here about it. http://forum.6502.org/viewtopic.php?f=2&t=5640