how should I identify that a key is pressed on keyboard in ARM?I want to input data when key is pressed on keyboard check whether it is valid or not for the RTC and if it is valid then change the time according to input data.Please provide an example showing above description.
It's your homework. You do it.
You check how a key is pressed in the same way with an ARM as with a PIC or a 8051 or an AVR. It's just how you access the processor pins that is different.