with 40 MHZ osc serin2 not work

[Pedro Santos]

Hello

My board with PIC 18F452 and lcd display without MAX232 device work fine with 16 MHZ cristal, but if I change the cristal to 40 MHZ the board work but not the serial communications with Serin2 comand don't work.
In the code I change to the Define OSC 40 instruction

Have anyone idea what I make wrong?

Thank You

Regards

Pedro

[paul borgmeier]

Maximum Crystal Frequency is 25 MHz - see datasheet
(this may be part of your problem)

[Pedro Santos]

Hello Paul

Thanks, I will try tomorrow

Thank You

Regards

Pedro

[Joe Rocci]

Maximum Crystal Frequency is 25 MHz - see datasheet
(this may be part of your problem)

Also, it's unlikely the oscillator was clocking at 40 MHz. Once you get past about 25 MHz, most crystals are designed for overtone operation. In order to get the oscillator to operate in the crystal's overtone mode, a special circuit is usually required.

Joe