Synchronous counters and PLCs
Logic operators - Sequential operators

We now look at how to implement sequential operators, whose outputs at a given time are a function of the present and previous states of the outputs. These sequential operators are made up of the presented flip-flops (D, T or JK ) and logic gates.

We deal first with counters, which are a special case of PLCs without inputs, and then with the general case of PLCs, which we illustrate with the example of a crossroads traffic light controller.

We consider only synchronous automata, where all flip-flops are controlled by the same clock signal. These are the most widely used because the operating condition boils down to satisfying the fundamental inequality that characterizes synchronous logic