Tom Sgouros <PICLIST@MITVMA.MIT.EDU> wrote:

> 1. I measured the actual rate of the RC oscillator, and found it to
> be 909091 Hz. If I put the scope probe on pin OSC1, I see a
> sawtooth wave. If I look on OSC2, I see a more-or-less square wave
> with the same period as the sawtooth. If I read my spec sheet, it
> says the frequency on OSC2 should be 1/4 times what I see on OSC1.
> What am I doing wrong here?

    Tom:

    You're probably loading down the oscillator with your scope
    probe; the only pin that's safe to look at with any old probe is
    OSC2.

> 2. I bought a 4 MHz crystal and some 22pF capacitors. When I insert
> these into the holes provided for their use on the board, I can
> only find a (very weak--fractions of a volt peak-to-peak) signal
> that gives me around 200 KHz. The signal is much weaker than it was
> for the RC oscillator, and doesn't look to me like a very healthy
> one either. It sort of has regular spikes, but I wouldn't call it a
> triangle wave or a sawtooth. (What shape does an oscillating
> crystal make?) I gather from some recent discussion on the subject
> that not all crystals are created alike, but shouldn't I at least
> be able to get close?

    Yes, but only if you've remembered to program the PIC's
    configuration bits for "XT Oscillator" mode.

    -Andy

Andrew Warren - fastfwd@ix.netcom.com
Fast Forward Engineering, Vista, California
http://www.geocities.com/SiliconValley/2499