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A win, sort of, but I’ll take it
Well the PCBs arrived and I decided to build up the CPU one slowly, not building the full thing. I’m glad I didn’t. Eventually after a lot of messing around with CPLD and ROM code I got something booting, it’s the Grant Searle ROM, but it worked. The sticking point seems to be serial comms. After much digging I discovered that the data on the data bus isn’t valid until 25nS after the clock edge, not a problem for older chips, but for the FT245 I’m using for the serial port it’s a problem. So after delaying the clock for the write a little I got some progress. So there…
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It’s been a month, or two
It’s been a while since I wrote, a lot has been going on. Firstly, the Transputer saga, I got a PCB from Oscar Toledo (https://github.com/nanochess/transputer) and confirmed that my TRAMs did indeed pass the tests with his card. However they did not with mine. Then I discovered that somehow none of my TRAMs worked with Oscar’s or my card. Very disheartening. So I’ve paused that for a while, there’s only so much failure you can take before you have to stop something for a bit. In the world of synths it seems things are slowing down globally, in part due to an orange womble in the USA. I have to…