Forward To The Past - 5
Single SteppingSo far, there's no reason why things should not just work. But what if there's a problem? Last night I was trying to work out why one of my address outputs didn't work right, and it occurred to me that since the Z80 is essentially a static processor, it would be pretty easy to add a single-step clock to our design so far.
All this requires is a 74LS00 a Single-Pole Double-Throw (SPST) pushbutton switch and a couple of resistors. Now, for each push of the switch we get one clock transition.
I will update the main schematic soon to reflect this change, and provide a way of selecting either option without rewiring, but since I'm working on breadboards, this is not too big a challenge to change over at the moment.
Another option would be to use a very low speed clock. We could either have a separate RC oscillator, or divide down the 8MHz signal to pretty much anything we like.
What would you rather see?