Hi
Thank you all for the support.
I have a RTC chip on board HT1380. I tried using it as a reference . I could do it but this implementation is having a major problem. The RTC chip needs a Oscillator enable command before use (i.e. it needs to be set ) and it requires 3 sec to stabilise the oscillator. This is not feasible as far as current application is concerned . It is difficult to do hardware changes as there are many unit in feild working on 11mhz. and i am giving new firmware which works on new boards(22Mhz ) and 11 Mhz. So i wanted to check if there is any other way than using RTC.