Oscillators

[Mihindu_gajaba]

Hi,

Hey guys i wanna know about Oscillators , as i know for PIC programing we're using Crystals right ?

ok the prob is,

i have read a tutorial and it says that The PIC has to be Connected with a 10MHZ Crystal to work ( because i'm using PIC16F84A - it doesn't have internal clock right ! ). as i know Crystal is doing it creates a pulse i mean it's just like this

One of the most commonly used oscillators is the pendulum of a clock. If you push on a pendulum to start it swinging, it will oscillate at some frequency -- it will swing back and forth a certain number of times per second. The length of the pendulum is the main thing that controls the frequency.
For something to oscillate, energy needs to move back and forth between two forms. For example, in a pendulum, energy moves between potential energy and kinetic energy. When the pendulum is at one end of its travel, its energy is all potential energy and it is ready to fall. When the pendulum is in the middle of its cycle, all of its potential energy turns into kinetic energy and the pendulum is moving as fast as it can. As the pendulum moves toward the other end of its swing, all the kinetic energy turns back into potential energy. This movement of energy between the two forms is what causes the oscillation.

Eventually, any physical oscillator stops moving because of friction. To keep it going, you have to add a little bit of energy on each cycle. In a pendulum clock, the energy that keeps the pendulum moving comes from the spring. The pendulum gets a little push on each stroke to make up for the energy it loses to friction

so can i use 4MHz crystal instead of 10 MHz.. Please help me..

and hey there is another thing hows RC ( Resisters and Cap ) acting like a Crystal..

Thnak You

Mihindu

 

[Nigel Goodwin]

so can i use 4MHz crystal instead of 10 MHz.. Please help me..

Yes, the PIC will accept a very wide range of crystals - but obviously it will only run at 40% speed, so the program needs to be written for the clock frequency you use.

and hey there is another thing hows RC ( Resisters and Cap ) acting like a Crystal..

It doesn't, it works as an RC oscillator - you should try reading the datasheet that explains all this!.

 

[Mihindu_gajaba]

Yes, the PIC will accept a very wide range of crystals - but obviously it will only run at 40% speed, so the program needs to be written for the clock frequency you use.


It doesn't, it works as an RC oscillator - you should try reading the datasheet that explains all this!.

Thanks Thanks Thanks. so that i have to change the Code right and hey i got an Crystal printed as 10.0000M is that the correct one.

 

[Nigel Goodwin]

Thanks Thanks Thanks. so that i have to change the Code right and hey i got an Crystal printed as 10.0000M is that the correct one.

Sounds like it!.

 

[Mihindu_gajaba]

Thanks

Sounds like it!.

Coooooooooooooool And Thanks ...

 

[matc]

Yeah, you can use 4MHz crystal if you want. Or you can use a resistor-capacitor as you say - set the configuration fuses and the PIC will know what to do in either case. It's all pretty clearly on the datasheet.

 

[Mihindu_gajaba]

Thanks