While I'd like to say my Z80 computer is working, after the last few days I'm completely expecting that it will have broken itself again by tomorrow. But for now it works.

One problem I had was a ridiculously noisy 5v supply. I'm not totally sure what fixed it. I added lots of capacitors all over the breadboard, which didn't seem to make any difference, and I removed a capacitor from the clock circuit. I think it was the capacitor removal which fixed the noise, but I'm not completely sure — especially since I don't really trust my oscilloscope.

Another thing I've done is added a nice LED array, which is neater than my previous LEDs, and givees me 8 debugging signals without having to do a lot of extra wiring.

As I said, the CMOS Z80 lets me drop the clock speed right down, so I dropped it down to 1Hz. It's really quite interesting watching the various control signals while the CPU runs at that speed, and it was showing that nearly everything was working properly — there were just some weird things happening with the signals coming from the FTDI.

As it's getting late at night, I couldn't be bothered to work out the timing, so I just put the clock speed back up to 4MHz, and now it seems to reliably read data from the PC over the FTDI link.

But who knows whether it wil still be playing ball tomorrow. If it works, I need to try and get the memory bank code working — at the moment it's hacked to always select the FTDI in all banks.