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Old 11th May 2018, 12:30 pm   #9
SiriusHardware
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Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,483
Default Re: Tesla MH74S571 programming.

In applications like this where one false move will ruin a one-shot chip I don't think it's a bad idea to have some hardware to limit things like pulse lengths to a safe maximum. The main thing is to consider what happens to the pins of the controlling uP during the reset / initialisation phase, and whether that will result in conflicting or unwanted signals like VPP being unintentionally enabled during that time.

I suppose the usual first line of defence is to have hold-off resistors which hold these things in a known state while the outputs of the uP are tri-state / undefined, but you often see schemes where a hardware gate is used between the controlling uP and the control circuit so that the uP has to output a definite pattern of enables - something which can't happen accidentally - in order to make something activate only when required.
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