F876 programming questions
Tony Nixon email (remove spam text)
Mike Mansheim wrote:
> >I activate VCC then a few 10's of millisecs later raise MCLR from ground
> >to ~13V. That's all you need to do. The 72 osc clocks will relate to the
> >reset feature in the chip. The OSC1 pin should be tied low (or high),
> >and not left floating, before and during the programming process to stop
> >any clock pulses incrementing the program counter.
> Tony, thanks for the response.
> When I do this "in-circuit", when I activate Vcc, MCLR will also rise to
> Vcc. Then I am raising MCLR from Vcc instead of from ground. Also, since
> the chip in installed on a target board, the OSC pins are hooked up, so I
> would think the chip would actually "run" for the period of time between
> activating Vcc and raising MCLR. This is the mode of operation I'm trying
> to get a handle on.
> Thanks again for the help.
This is why I included an open collector output for ICSP on my new
programmer design. This goes low during programming and can be used to
pull the OSC1 or RB3 pin low.
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