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PIC16F877a i dont have cyrstal oscillator, can I use external clock instead?

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eebhoi01

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Hello Guys,


Please teach how to connect external clock to PIC16F877a since i dont have crystal oscillator available.


Thanks.
 

Hi,

Its all detailed with diagrams in the 877a Datasheet - Oscillator Section.

You can also use a resistor and capactitor instead of a crystal, although the accuaracy will not be great, it will get you going.
 

you got to set the config bit as ( FOSC1:FOSC0: Oscillator Selection bits)( page # 143 in datasheets) : 11
and the Resistor and cap (Recommended values: 3 k ≤ Res ≤ 100 k C > 20 pF) must be connected b/w the VDD and Gnd. and then to OSC1 of the PIC. refer page 146.
Cheers!
 
You can even try it without the 20pF capacitor to get the maximum frequency. Note you are relying on the capacitance of the socket and board and is not guaranteed to work, although it works on my board. Don't forget to set the FOSC1:FOSC0: Oscillator Selection bits to XTAL oscillator.
 

I really appreciate your help guys, now in know where to go. Im currently reading the oscillator portion of the datasheet. Ill give an update on my progress. ^_^ THANK YOU
 

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