• Timers are there to count the internal clock Pulses of a Micro controller.
  • Counters are there to count the external pulses.
States of a Timer
  • Reset
  • Initial State
  • Running
  • Blocked
  • Finished
  • Overflow
Uses of a Timer
  • Event driven(initiate an event after a delay)
  • Scheduling of Tasks in a System (by activating and running a timer)
  • Watchdog Timer (Resets the system after a predefine time)
  • Real Time clock (A clock that never stops and keeps on running and never be reset, Eg. Heart Beat)
  • Time slicing of various tasks.
There are two types of timer

Hardware Timer
  1. Atleast one hardware should be available in a Microcontroller.
  2. The figure above shows the Hardware Timer has the control bits
  • Timer Enable
  • Timer Start
  • Timer Stop
  • Pre scaling bits
  • Up count enable
  • Down count disable
  • Load Enable
  • Timer Interrupt Enable


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