piclist 2001\01\29\173351a >
Thread: F876 programming questions
picon face BY : 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.

Best regards



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