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Old 29th Nov 2022, 9:18 pm   #36
SiriusHardware
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Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,482
Default Re: Tesla Programmer

Quote:
Are the proms hot pluggable?
I would not like to assume so. 'Proper' (ie, £900) programmers switch all the signals, including power, on and off at the beginning and end of the programming sequence. I think it would be a case of fitting the PROM, powering up the programmer, programming, powering down the programmer, removing the PROM (to be on the safe side).

Quote:
watch out for outputs from microcontrollers or interface ICs floating or pulsed high/low during power up or reset.
I notice Chris's circuit has pulldown or pullup resistors which are intended to hold the various programmer control lines in the off state during that initial phase, the reason being that the 8255 will start up with all of its I/O pins in input mode until otherwise configured. The resistors hold the control lines in their inactive states until they are intentionally driven to their active state by their associated 8255 pins.
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