What is your oscillator config ?
Any 100 nF cap near the PIC ?
Any I/O pins configurated as inputs but left unconnected ?
How is MCLR connected ?
Anything else you haven't told us ?

Regards,
Jan-Erik.


> -----Original Message-----
> From: piclist-bounces@mit.edu 
> [mailto:piclist-bounces@mit.edu]On Behalf
> Of Bill Kuncicky
> Sent: den 9 april 2006 18:41
> To: piclist@mit.edu
> Subject: [PIC] What are the symptoms of oscillation?
> 
> 
> This is kind of a dumb question, but I'm not sure how to 
> phrase it better.
> :-(  I've built up a little circuit, using stripboard, which 
> has quite a few
> point-to-point wires soldered on it.  There is a 9-volt power 
> input, which
> goes to a 7805 which has a .3 uf capacitor from input to 
> ground and a .1 uf
> capacitor from output to ground, as recommended by the spec 
> sheet.  I wired
> in an 18-pin socket, checked Vdd and Vss with a multimeter, 
> and it has about
> 5.12 volts.  There is a single LED on the board, with a 1K 
> resistor from one
> of the output pins to the LED (and then to ground).
> 
> I wrote a little "blink an LED" program and programmed the 
> 16F628 with the
> Wisp628.  So far, so good.  It runs, and the LED blinks like a 
champ.
> Except . . . every now and then, the light of the LED will 
> just begin to
> quiver, rather than blinking on and off, as if someone mashed down 
the
> accelerator hard!  When that happens, the PIC gets very hot.
> 
> I've checked the wiring carefully, and don't see anything 
> wrong.  Don't see
> any solder problems.  When it runs, it runs fine, until it goes into
> overdrive.  Could this be the PIC going into oscillation?  I 
> don't really
> know what that term means when applied to a PIC, but cannot 
> figure out what
> else could be causing this.
> 
> Thanks for any advice.
> 
> Bill
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