Derrick Early wrote:

> I had trouble with a capital T when trying to program in-circuit with
> the oscillator running.  The program would intermittently load starting
> at the wrong place.

One of my students found exactly this behaviour recently (he was using
an Xtal oscillator if it makes any difference).  He was using O/C
buffers to drive RB6/7 and had a sort of wire-OR arrangement of two
transistor switches to set VPP/MCLR to one of 0, 5V or 13V.  The program
seemed to be loaded a few bytes displaced from where it should have been.
Nothing was repeatable though.  The cure was a 10K//100pF network from
MCLR to GND.  The MCLR line is incredibly sensitive.

David
--
david.tait@man.ac.uk