It works on a Zaccaria Invaders PCB, as I have used it on a few of those before. mind you these are nice and simple, no pages as everything fits into the first 2k !!
On 19 September 2017 at 06:12 David Gersic <info@zaccaria-pinball.com> wrote:
On Sunday, September 17, 2017 12:24:07 PM Ian Eure wrote:
That's not really how it works. The CPU in the pod is driven by the clock on the PCB. If the pod CPU was running at a different clock speed, nothing would work at all.
Hm. So the adapter ports CLOCK straight across, from Z80 pin 6 so 2650 pin 38. The Z80, being capable of running at faster clock speeds, should be perfectly happy to run slower.
Based on the article, it sounds like perhaps the adapter just doesn't match the timings of the original CPU to support anything other than individual reads, or perhaps there's an issue with your adapter. I'd see if anyone else has used a similar setup and see what results they got.
The old Fluke article seems like they were trying to match the timings, or at least get close enough. Maybe they were good enough for whatever it was they were testing when the article was written.
I don't know anybody else that works on Zaccaria boards, so no, haven't got anybody else that can confirm or deny that this works at all.
If you wanted to slow things down in the hopes of improving marginal timings, you'd need to alter the clock on the PCB, either by substituting a slowre crystal or by replacing the clock that controls the CPU and bus accesses with a slower signal. Either option almost certainly guarantees that the video hardware won't work, and may mask other problems going on with the board.
Right now, I'm testing on boards that I know to be good. I could try swapping in a slower crystal to see what happens, good or bad. But if the pod runs at UUT clock speed, I'm thinking that wouldn't be likely to make a difference.
Are you aware of Paul Swan's 2650 tester? That might be another option worth looking into. http://www.paulswan.me/arcade/ArduinoMegaICT.htm
Yes, I've seen that too.
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