Programmable interval Timer 8253

 Programmable interval Timer 8253

Function and working principle of 8253:

•The 8253/54 solves one of most common problem in any microcomputer system, the generation of accurate time delays under software control.

•Instead of setting up timing loops in system software, the programmer configures the 8253/54 to match his requirements, initializes one of the counters of the 8253/54 with the desired quantity, then upon command the 8253/54 will count out the delay and interrupt the CPU when it has completed its tasks.

•It is easy to see that the software overhead is minimum and that multiple delays can be easily be maintained by assignment of priority levels.

•The 8253/54 includes three identical 16 bit counters that can operate independently.

•To operate a counter, a 16-bit count is loaded in its register and, on command, it begins to decrement the count until it reaches 0.

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