How can there be a replacement for the old pulse counter in the past?

The counting constant is the key parameter used by 8253 to count. The 8253 has 3 independent counting channels with a minus 1 counting method. When the gating signal is active, the channel counts once for every 1 counting pulse input.

A count becomes timed when the count pulse is a clock signal with a known period. When a channel is used as a counter, the number of counts required should be preset to the counter of the channel, and the counted events should be input from the CLK terminal in the form of pulses, and each time a counting pulse is entered, the counter content is reduced by 1 place, and the value to be counted is counted to 0 place.

There will be an output on the out side. Indicates that the number of counts has arrived. When a channel is used as a timer.

A clock pulse of a certain frequency is input by the CLK. Determine the desired count value based on the length of time required to be timed. And preset to the counter, each time a clock pulse is entered, the counter content is reduced by 1 place, and the value to be counted is counted to 0 place.

out will have an output indicating that the timer time has arrived. The clock frequency allowed to input from the CLK is in the range of 1 2MHz. Therefore, the internal operation of either channel as a counter or as a timer is exactly the same, except that the former is counted by the counting pulse by ticking 1.

The latter is an inner clock pulse that is counted by 1 tick.

When used as a counter, the number of counts required can be directly preset into the deceased 1 counter as the initial value of the counter. When making a timer, the initial value of the counter, that is, the timing coefficient, should be calculated according to the required timing time by the following calculations: Timing coefficient The time that needs to be timed The clock pulse period In fact, the counting constant = the timing count = the initial value of the count.

The calculation is the same.

The counter input is a pulse signal, which used to be mechanical, but now it is digital, and I have replaced it with a Hongrun counter.

There are many types of counters. According to whether the triggers of each answer hand in the composition counter use a clock pulse source, it can be divided into synchronous counter and asynchronous counter; According to the different carry system, it can be divided into binary counter debate, decimal counter and arbitrary counter; According to the difference of the number increase and decrease trend in the counting process, it can be divided into addition counter, subtraction counter and reversible counter. There are also pre-made numbers and programmable counters, and so on.

Its basic function is to detect the number of clock pulses, that is, to achieve counting operations, it can also be used to divide the frequency, timing, generate beat pulses and pulse trains, etc. For example, counters are used in timing generators, dividers, instruction counters, and so on in computers.