Waveform at xtal2 pin of AT89S51

[saraheem]

Hi...

I am using AT89S51 uC. When i connected the circuits as per the schematics in one website, i got a sinusoidal waveform at xtal2 pin of the uC. Is it correct??? Or should i be getting a square wave? Also that schematic didn't use any parallel capacitors between the xtal 1 & xtal2 pins as given in the datasheet of the uC.

 

[IanP]

A square wave has infinite spectrum, but a crystal can vibrate only at specific frequencies (fundamental, third or fifth overtone, ..) ..
So, it has to be a sine wave and, as you experienced by yourself, it is a sine wave ..

As far as capacitors around crystal are concerned, in the AT89S51 case there is no parallel capacitor between Xtal1 and Xtal2, but the data sheet specifies two burden capacitors as to be around 30pF .. see attached picture ..

Rgds,
IanP

 

[saraheem]

Hi IanP...


Thank you for confirming that... I was doubtful since i had trouble programming it earlier...