I have 4mhz crystal oscillator connected to a micro(16f946) with 27pf on both its legs.
How do I know that its working the right way?
I put a probe on it and I looked at the signal, it looks something like a sinewave but not exactly like one.
Can someone please explain.

Thanks for your response.
I understood from your response that a 4mhz crystal gives a 1Mhz internal clock frequency.( do all the pic's cut it by 4?)
Actual Frequency=so internal clk frequency /256=3906.25Hertz
1/3906.25=256uS is the time period?

Can you please explain, I would like to know what a 4Mhz with 27pf signal on the scope should look like?(sine wave?)

Is the amplitude of waveform controlled by Vdd ?
For this particular chip it says 20Mhz oscillator clock input on the datasheet. what does this mean?

Originally Posted by Angy

I have 4mhz crystal oscillator connected to a micro(16f946) with 27pf on both its legs.
How do I know that its working the right way?
I put a probe on it and I looked at the signal, it looks something like a sinewave but not exactly like one.
Can someone please explain.

As long as you are getting a rising edge thing should be fine. If your signal looks a bit like a sine wave, that is just because it is taking time to rise....

Yes, all PICs divide the oscillator input by 4. See any data sheet....
for why.

There is a difference between a crystal - like what you have with two pins, which needs a small capacitor on each leg to ground... and uses the PIC's internal hardware to create an oscillator. You can also clock a PIC with an oscillator, which is a self contained oscillator in a can. These usually have four legs, and put out a fairly strong signal, as opposed to the signal you will read from a leg of the crystal.

If I have some time today, I'll scope one and post the picture.

Jason,
The helpful illustration of how the clock divider works with instruction pipe lining would be a good one to include here too. Do you know which illustration I'm referring to?

That's the one! Thanks.

Thank you all for your suggestions, I appreciate your help.

I'm just going to assume that the oscillator is working right.
Now the actual problem I'm facing is with the AD converter.
When I simulate the software I get the error below, I already looked the same thread on this website but they did not give the solution.
ADC-W0008: No stimulus file attached to ADRESL for A/D.
so as the warning say no stimulus is attached to address register where the a/d value is stored.so can someone explain what I'm doing wrong?

Thanks.