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Slothie · 11th May 2018, 12:59 pm

When I was 17 I built an interface for my PET to a paper tape punch (basically a 9 channel solenoid driver which coincidentally I unearthed in mums loft recently), and in the first version of the hardware I discovered that if you didnt have the software running before powering up the interface then it would spew out tape at an alarming rate! I changed the interface so that a logic '1' switched off the solenoid, since the user port defaulted to inputs with a weak pull-up, so I have learnt this lesson!

I think that I'd do something similar, so I have to drive a pin to 0v to switch on the programming voltage, with some kind of power on delay so that the Vcc pin of the prom cannot be driven until the reset process has completed. In any case I'd be checking all the waveform outputs carefully on the oscilloscope before an actual prom gets anywhere near it! Somewhere I have one of those cheap Chinese USB logic analysers which I may dig out from wherever I hid it, which might be useful to record waveforms during power up and programming cycles etc.

11th May 2018, 12:59 pm	#10
Slothie Octode Join Date: Apr 2018 Location: Newbury, Berkshire, UK. Posts: 1,287	Re: Tesla MH74S571 programming. When I was 17 I built an interface for my PET to a paper tape punch (basically a 9 channel solenoid driver which coincidentally I unearthed in mums loft recently), and in the first version of the hardware I discovered that if you didnt have the software running before powering up the interface then it would spew out tape at an alarming rate! I changed the interface so that a logic '1' switched off the solenoid, since the user port defaulted to inputs with a weak pull-up, so I have learnt this lesson! I think that I'd do something similar, so I have to drive a pin to 0v to switch on the programming voltage, with some kind of power on delay so that the Vcc pin of the prom cannot be driven until the reset process has completed. In any case I'd be checking all the waveform outputs carefully on the oscilloscope before an actual prom gets anywhere near it! Somewhere I have one of those cheap Chinese USB logic analysers which I may dig out from wherever I hid it, which might be useful to record waveforms during power up and programming cycles etc.