Make sure the crystal is on the same strip as the OSC pins (don't run wires
to it). Try it without any capacitors (I am running a 16C73A at 20 mHz on my
solderless breadboard and it runs just fine - no bypass caps needed).  The
breadboards have a lot of capacitance all by themselves.

I tried moving the crystal away from the chip and it choked.  So, put the
thing on a couple of header pins and plug it in as close to the chip leads
as possible.

Dan


-----Original Message-----
From: Matthew Fries <freeze@VISI.COM>
To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
Date: Friday, September 03, 1999 10:21 AM
Subject: PIC Newbie question


>Here is a tricky situation: I cannot seem to get any of my 16F84-10/P PICs
>to run using a crystal. The code simulates nicely in MPLAB, and I can get
>the same code to run if I use the RC setting and components, but not a
crystal.
>
>I have tried 4Mhz, 6Mhz and 10Mhz crystals.
>I am using the two capacitors (one on each leg of the xtal) which are 22pf
each.
>Vdd is 3v. I have tried 5v.
>I have tried 2 different solderless breadboards. An old radio shack one and
>a brand new one from JDR.
>The wdt is DISABLED.
>OST is disabled.
>PWRT is disabled.
>MCLR is high
>
>
>The spec sheet refers to serial and parallel resistive crystals. How can I
>tell what kind I have. There are no useful markings on the xtals (other
than
>the frequency and the mfgr).
>
>Is there some excess capacitance in the breadboard that is keeping the
>crystal from oscillating?
>Should I enable the OST?
>Or maybe the PWRT?
>
>Any suggestions? I didn't think it would be this difficult.
>
>
>Remove the BALONEY from my email address.
>-----------------------------------------------------
>Matthew Fries       Minneapolis, MN    USA
>freeze@baloneyvisi.com
>
>"Quit eating all my *STUFF*!" - The Tick