Write in detail about the working of the 8253 programmable interval timer
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Answer:
The Intel 8253 and 8254 are Programmable Interval Timers (PTIs) designed for microprocessors to perform timing and counting functions using three 16-bit registers. Each counter has 2 input pins, i.e. Clock & Gate, and 1 pin for “OUT” output. To operate a counter, a 16-bit count is loaded in its register. On command, it begins to decrement the count until it reaches 0, then it generates a pulse that can be used to interrupt the CPU.
>The most prominent features of 8253/54 are as follows −
1. It has three independent 16-bit down counters.
2. It can handle inputs from DC to 10 MHz.
3. These three counters can be programmed for either binary or BCD count.
4. It is compatible with almost all microprocessors.
5. 8254 has a powerful command called READ BACK command, which allows the user to check the count value, the programmed mode, the current mode, and the current status of the counter.