clock problems

[desai]

I have been using an external 20 MHz clock with my pic 16f874.

Now i wanto change the frequency to 4 MHZ and I changed the code as follows

#use delay(clock=4000000) and the pin from clock is going to 13 of the PIC.

It dosent seem to work as when i check with the scope i see about 450 Hz signal (and not MHz)

do i need to change this line of code too?
#fuses HS


PLEASE HELP .

Thanks

[PCM programmer]

When you say "external clock", I assume you are using the metal "can"
type of oscillator. It looks like this:
http://rocky.digikey.com/WebLib/Abracon/Web%20Photos/ACO%20SERIES.jpg
Is that correct ?

If so, disconnect the 4 MHz oscillator from the PIC and look at
the output pin with your oscilloscope. If the oscillator is correctly
connected to power and ground, you should see a 4 MHz square wave
on the output pin.

---------
If you're using a crystal, then it will look something like this:
http://rocky.digikey.com/WebLib/ECS/Web%20Photos/HC-49US.jpg

[desai]

yep the shiny metal kinnda clock like the one in the picture with 4 pins.

Sorry i assumed that the clock and x-tal were the same things.

I dont have a 4 MHz clock I just have a 20 MHz clock. But is there a way to divide 20 MHz clock to be used as a 4 MHz clock.

I thought PIC 16F874 had an internal clock of 4 MHz but did not see anything like that on the data sheet anywhere.

[PCM programmer]

You would have to use an external divide-by-5 circuit.
It's easier just to buy a 4 MHz oscillator.