blink led program in pic18F8722

[hemnath]

Thank for helping me to solve the issue.

The board has a onboard 20Mhz crystal. Please have a look into that link. I am not wiring from the header pins RA6 and RA7.

I think the pins RA6 and RA7 in the header are used for, if the crystal is not used, the pins can be used as I/O pins.

I have double checked the traces from the crystal to micro-controller pins with an ohmmeter. continuity is present.

May be a faulty crystal condition as suggested by Ttlemah, So i changed the crystal and capacitors also.

LED blinks when I use the internal oscillator. But not for external crystal.

In the datasheet, on crystal configuration page, it is recommended to use 330Ohms resistor and also suggested by Ttelmah, I used those values. Still no blinking. Also I have changed the resistor values by trial and error. Still no improvement.

Please help.

[PCM programmer]

[hemnath]

I have connected a LED with a series resistor of 330 Ohms from header RD0 pin.

[Ttelmah]

It is the long runs to the external header that has us worried. Problem is that the track capacitance will almost certainly exceed the required crystal capacitance....
Also the long tracks make a whisker more and more likely. Have you tested with an ohmmeter. You need to sit down, and verify that there is no connection between the crystal pins themselves, and then that there is no connection to _every_ track that runs close to the line. _Every_ track. Also that there is a physical connection from the PIC pins to the crystal.

[hemnath]

Yes I checked every trace with an ohmmeter.

I cut the trace from header to crystal. The trace is get separated now. Now the connections is established from crystal to micro-controller pins. Also checked the connections from capacitors also.