Watchdog timer

Microcontrollers contain timers. Some of them contain two types of timer and some five types. The five types of timer are watchdog timer, basic timer, real time clock, timer A and timer B. A watchdog timer protects the system against software malfunctions. It can also be used as an interval timer, if system is not required of any protection. Watchdog timer operation is controlled by a 16 bit register WDTCTL. The microcontroller is also contains a watchdog counter which is invisible to the user and is a 16 bit register WDTCNT. The watchdog become active once the microcontroller is reset. If the watchdog is in running mode, counter should be cleared every time to prevent it counting to limit values. This task is known as petting, kicking or feeding the dog.  Normally a microcontroller resets itself whenever the watchdog counter reaches its limit. A basic timer provides the clock for the LCD module and thus generates periodic interrupts. A real time clock is used for the counting of seconds, minutes, hours, days, months and years. Timer A is a general purpose timer. Timer B is provided on large microcontrollers.