>>Have you tried an external pullup on the / MCLR pin? I just added a 4.7Kohm pull-up resistor between the MCLR pin and 5 volts. Now the led stays on all the time. If I put my thumb (finger) on top of the pic there is no longer any oscillation. Ed ----- Original Message ----- From: To: "Microcontroller discussion list - Public." Sent: Tuesday, November 23, 2004 4:39 PM Subject: Re: [EE]: 12C508A with Xtal Won't Oscillate > > Have you tried an external pullup on the / MCLR pin? > RP > > > ----- Original Message ----- > From: > To: "Microcontroller discussion list - Public." > Sent: Tuesday, November 23, 2004 3:08 PM > Subject: Re: [EE]: 12C508A with Xtal Won't Oscillate > > >> >> Is it touching the micro that makes it work, or shading it. JW parts >> should normally be run with the window covered anyway. > > The window is now covered by light blocking double faced tape. The led is > on > solid. Putting my thumb on the tape causes it to appear to operate (led > flashes without sync signal). > >> If it's the touching that's doing it then it's likely to be the injected >> noise. Check your decoupling on the power feed to the micro is connected > >> OK and as close as possible to the power pins on the chip. > > Done. I have a 0.1 uF and a 10 uF tantalum bypass capacitors across the > pin > > 1 and pin 8, literally. The power supply is well bypassed with 2 > regulators. > The firs regulates the 12 volts and the second, off the 12 volt regulator, > is a LM2940-5.0 for 5 volts. Both check out fine. > > > > > > _______________________________________________ > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist _______________________________________________ http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist