I was able to get my Rockwell R65C51 to connect using an HC-05 with no trouble. I did add a voltage divider to the RXD line to drop the 5v down to ~3.3v to play it safe, but it did work at the full 5v when I did a quick test. I'm still trying to get an HM-10 (V4.0 BLE vs. V2.0) to work, but it hasn ...

With some head scratching, I finally got my Cylon assembly code modified to run in EhBASIC! Now that I have a functioning board, let the fun begin!

When in doubt, a shotgun approach is always a valid option, even if it's not an elegant one! I got in the CY62256N SRAM chip today and swap it in for the AS6C62256, without changing any of the wiring, and things are now working as expected. That'll teach me to order parts for someone else's design ...

oscillator seen in the photo fail to confirm it meets the specified input requirement on a WDC CPU
I added the pull-up resistor to the oscillator output and it made no difference.

Phi2 inputs on the VIA and ACIA also connect to the oscillator (not the CPU PHI2O output on pin 39)
I moved the ...

Just attempted 8000 and 4000 and both would either result in "Memory Size ?" coming up again or system lockup.

My understanding of Chris's design is that the 32k SRAM is divided up so half is for the OS, and then the other half is for the ACIA, VIA and the remainder for use as potential I/O space in a future revision. I'm completely new to all this so my grasp of how it all ties together is almost zero, so ...

Here are the two data sheets. The note was just to head off any questions if I had wired up the AS6C62256 using the pinout of the CY62256N, which would cause all sorts of issues!

A note on the SRAM swap... I did wire it up using the AS6C62256 pinout vs. CY62256N as they are not the same.

I swapped in the 74HC00N for the 74LS138N with the same results. A hardware (wiring) issue is totally possible as this is my first major point-to-point wiring job. I've Ohm'd out the board a few time to verify it matches the schematic and even picked up a cheap logic probe to make sure I didn't have ...

I've been powering it directly from the 5v FTDI cable that I'm using for communication with my computer. I've also tested it out with a 5v 2.5A cellphone supply that I modified with the same result. I have gone through Garth's primer, that is where I got the circuit for the 555 RST and also the ...

Thanks for the pointers! Always interesting following someone else's design when you don't fully have a grasp of the overall design, but it makes for a good learning experience!

I did use a 1mHz can oscillator connected to pin 37 of the 65c02. I've got an 74HC00 coming and will try that out using ...

Completed building up a 6502 SBC using this design. https://github.com/chrisabird/sbc65

I assembled his test code using cc65 to test out the VIA and the ACIA and they are working fine. I can modify the VIA code and can adjust the ACIA baud rate without any issue so the SBC appears to be fine ...