Hi,

Sorry, I forgot to take some pictures

Yes, I simply soldered female headers on the pcb 0.1 inch wider and made a simple perfboard with the socket for the 6522 and pin headers to connect to it.

I pushed the male pins all the way so I can solder both the socket and pins on the same side of the ...

Hi,

Finally the new PCB has arrived! It connects to the existing board using some pin headers

The new expansion board have these:

- Up to three 65C22, stacked, the last one don't have the i/o ports populated on the PCB, so I have to put it on their own perfboard

- Up to two 65C51, stacked too ...

Hi,

The 65c51 arrived yesterday and it is running fine! :D

For the moment, as I don't have some glue logic IC's yet (74HC30 and 74HC138) to do Daryl's SBC 2.5 address decoding and now I am only using one I/O IC I am using the one that Garth shows in his primer, modified for my system ...

Awesome work!

Love the front panel too

The CMOS 6502 can be clocked as slow as you need stopping it during phi2 high, I drove it that mode while doing my SBC to test it, and see the address bus data was critical to make it work.

It's the best thing you can do to find the problems, there are lot ...

Hi,

I've been thinking and designing the schema of the new board to upgrade the computer and I'm waiting now to the new parts to arrive.

It will be on top of my current board and I had decided to maintain the ATMega instead of the new parallel flash, the reason: while thinking in how to develop ...

Maybe there's a problem with whatever is driving NMI, meaning the problem or damage is not in the processor itself.

I don't think so because I have leave NMI line with only the 3k3 pull-up resistor and I'm measuring voltage on this and getting around 1.5V when in that case it should return about ...

For others' benefit, the new(ish) page on it is at http://wilsonminesco.com/BenchCPU/ .

What a reading, I will try to translate it to spanish for my father, he'll be impressed.

I bought yesterday a pair of R65C51P2 on ebay, I would had prefer a 4Mhz part but couldn't find it at good price ...

As you're starting to change the basic design to remove the ATMega, might I suggest using a PLD as a single glue chip. This will give you more flexibility overall. As I found the bug in the recently released WDC W65C51 ACIA, I eventually replaced it with a NXP SCC2691 UART (older single channel ...

Hi,

The 16C550 it is maybe one of the best options to try with, anyway I think I will try to find an old stock 6551 because I believe it's good to have a couple of them.

Had readed the post regarding 28L91/92 but I think it is too complex for a first time design.


For the next versions, let me ...

ACIA 6551
Unless you have an old stock one knocking around, don't bother. The currently available WDC 6551 has a severe bug in it, see this topic .


Yes! I had read that and it's my main problem to drop out the ATMega


With the I2C modules, are they connected via the atmega, or do you have ...

Hi,

I am Angel and this is my very first post, I have been reading this forum since a couple of years and I like to show you my first SBC which I built past year.

In the 80's my father had a Commodore 64, about 15 years ago I made an emulator of that computer, since then I like all the things ...