Forward To The Past - 5

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Single Stepping

So 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?

Location: Sydney NSW, Australia

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