need explanation of avr different clock option

[vishu489]

now i'm having new question what is the use of osccal reg ? i know it is related with internal calibrated RC oscillator , i also read datasheet but i can't understand it properly. one more question can anyone explain me how crystal oscillator circuit works? what is the use of loading capacitor and how to calculate it?

 

[Tahmid]

Please go through this: www.atmel.com/Images/doc2555.pdf

Hope this helps.
Tahmid.

 

[vishu489]

sorry for late reply , if i'm getting correctly in avr there is internal rc crystal option which can be tuned to 1,2,4,8 Mhz . but interms of accuracy its poor ,we can't use it where we required high percentage of accuracy. frequency of internal oscillator get affected by variation in supply voltage and temperature as per given in uc characterstics explanation so to provide compensation over that we need to configure osccal reg. also the value which we have to load is device specific and i think its varies from one device to another device . so for configuring oscal reg we have to read oscal byte at the time of programming and then we can add it to our source code.

so please tell me am i right or wrong??