Boards arrived Monday and I’ve spent a little time each evening working on bringing up the first. There was a horrible error in one of the CAD libraries I used, resulting in power supply connections being reversed, so a new part has to be created before the next board spin.
Tonight the CPU was running code in the main EEPROM! The top trace is the 6502 clock and the bottom is the SYNC line, which goes high every cycle where the processor is reading an opcode. The program is a JMP $ (jump to itself) so the timing is going to be exactly the same all the time:
Yes, that’s a very old analog scope. It’s got one of those “tube” things! The traces are usually sharper but the power supply powering the KIM Clone is sitting on top of the scope, so that causes some magnetic blurring of the image.
And this is the board partially built and running on my workbench:
The processor is running, address decoding works, the expansion EEPROM works, and the super-bright power-on LED is working. I’ll turn down the brightness for the final board, but I did want to use a blue LED on something 🙂
The next step is to insert the RAM and make it works, then get the USB chip soldered on and make sure it works. For what it’s worth, the hard part and mostly likely source of errors will be the decoding for the 6532s, keyboard, and LEDs. It’s a good start but there is a lot to test.