A timer is a simple counter! The input clock of microcontroller and operation of the timer is independent of the program execution.All the Atmel microcontrollers have Timers as an inbuilt peripheral.
To see the interrupts occurring on your system, run the command: # watch -n1 "cat /proc/interrupts" CPU0 CPU1 0: 330 0 IO-APIC-edge timer 1: 11336 0 IO-APIC-edge i8042 4: 2 0 IO-APIC-edge 6: 3 0 ...