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Old 17th Sep 2020, 10:32 pm   #48
Buzby123's Avatar
Join Date: Oct 2011
Location: Culcheth, Cheshire, UK.
Posts: 406
Default Re: I found it !. A very sorry looking MK14

I didn't realise that the address pins were occasionally 'floating', so it seems like my screenshots might not be as bad as what they look like.

But are all the address lines being driven at any time ?. I don't what areas the code is accessing.

What I need now is the gadget I built a hundred years ago, the 'NOPulator' !.

This was a gadget I built when I was working for an arcade machine company, fault finding in things like Space Invaders and pinball machines.

Finding faults in the address decoders was a PITA, until I built the NOPulator.

This was a Z80 CPU mounted on a 40 pin DIL, which plugged in where the original Z80 should be.

The Z80 on the NOPulator had it's data pins 'bent up' and they were hard-wired as a NOP. This made the Z80 run through the whole address range repeatedly, executing NOPs at every memory location.

A tiny switch gated the RDstrobe from the Z80 to either RD or WR on the socket, so the NOPulator would either read or write the whole memory range.

What I need now is a NOPulator based on an 8060.
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