Wouter van Ooijen wrote:
>
> > I've read the 16F628 datasheet but i'm still in the
> > dark about one thing; if I do HVP ICSP using MCLR,
> > and program the PIC to have the MCLR pin as an IO
> > pin (ie set it to internal MCLR), can I then reprogram
> > it *again* at a later date using HVP ICSP MCLR??
>
> The *latest* programming specs for all PICs (not the original 16f628
> programming spec!) that allow MCLR to be used as IO pin require an
> enter-programming sequence where Vpp is applied *before* Vdd, so the
> part can be re-programmed using HVP whatever the MCLR pin is configured
> for. I dunno about LVP. The normal sequence (Vdd first, the Vpp) will
> work most of the time, but often fails (at least on 12f628) when MCLR is
> configured as IO.


Thank you Wouter! :o) Trouble is that this is for
ICSP, so if Vpp is VHH first my Vdd has a slow (150mS)
rise time as the circuit is attached. :o(
-Roman

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