> -----Original Message-----
> From: Alan B. Pearce [SMTP:A.B.Pearce@RL.AC.UK]
> Sent: Tuesday, March 12, 2002 8:29 AM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: [PIC]: In Circuit Programming - 16F877 using MCLR only
>
> >I suppose with checksums etc it should be doable.
> >
> >I was wondering if you would have more luck clocking the OSC1 pin after
> >a reset.
> >
> >That way it's possible to know exactly what code your boot loader should
> >be executing.
> >
> >You might get faster transfers knowing this.
>
> How about moving the goal posts slightly. Use a timed reset to put the
> device into programming mode as per someone's 3/4 sec - 1sec suggestion,
> and
> then the programming code uses normal pins to do the communication, e.g.
> the
> on board uart, or it could be any pair of pins.
>
> Using this method one could also have a "timed reset to enter ICD mode" :)
>
I've been following this thread with interest, a bootloader that just uses
MCLR is very appealing.  However, I can't see how the bootloader would
differentiate a valid reset (from e.g. a rest button or supervisor) from a
bootloading attempt.  If you have to use another pin to test for "run" or
"bootloader" mode, then the whole thing seems a little pointless and you may
as well use an existing loader.  Of course it's more than likely I'm missing
something blatantly obvious.

Cheers

Mike

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