The principle is that the gate circuit is controlled by the shaping signal with B channel input frequency fB, that is, one pulse opens the door and then another pulse closes it. The time interval (TB) between two pulses is the door opening time. The pulse group with the shaping frequency fA input from channel A passes through the door within the door opening time, so that the counter counts, and the count value n = fa TB.

In the digital system, the counter mainly counts the number of pulses, which consists of a basic counting unit and some control gates. The counting unit consists of a series of flip-flops with the function of storing information, such as RS flip-flop, T flip-flop, D flip-flop and JK flip-flop.

The counter at the addition and subtraction control end increments when the level is low; When it is at high level, the counter counts down. When used as an addition counter, QD output can be used as a ten-divider, QC output can be used as an eight-divider, QB output can be used as a four-divider, and QA output can be used as a two-divider.

Extended data:

Counters are widely used in digital systems, such as counting instruction addresses in the controller of an electronic computer to take out the next instruction in sequence, recording the number of additions and subtractions in multiplication and division in an arithmetic unit, and counting pulses in a digital instrument.

Counter can be used to display the working status of products. Generally speaking, it is mainly used to indicate how many copies of folding and matching work have been completed. Its main index lies in the number of digits of the counter, generally 3 digits and 4 digits. Obviously, a 3-bit counter can display 999 at most, and a 4-bit counter can display nine thousand nine hundred and ninety-nine at most.

Baidu encyclopedia-counter

Baidu encyclopedia-electronic counter