At 10:06 PM 2/24/2004 -0500, you wrote:
>Hi All:
>
>    I'm just starting out with PIC's, and have breadboarded
>a 16F877 with an oscillator composed of a 4Mhz parallel-cut crystal, and
>15pf caps.  When I scope out OSC1 and OSC1, I don't see any
>oscillation.  I've tried a range of caps from 12 to 33pf.
>
>    The 16F877 is straight from the distributor - completely
>unprogrammed, since I haven't built a programmer yet.  ;-)
>
>    My question is:  Should I be seeing oscillation under these
>conditions?  Or do the configuration fuses need to be programmed first,
>before the oscillator will start?

Typically they come set to ext RC oscillator, so if you put one of
those on there you should see oscillation. You also have to
pull /MCLR high in the case of the ext RC.

You may only be able to see oscillation on OSC2 because your oscilloscope
loads OSC1 too much, in the case of the crystal oscillator.

Best regards,

Spehro Pefhany --"it's the network..."            "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

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