sequential logic circuits covered in the main text of this blog are studied in college courses than from the point of view a little more formal, using a slightly more elegant language. In fact, we are talking about the same. There is no introduction of new design techniques that we consider essential to what we can achieve with what we have already covered. Anyway, this article aims to fill this perspective a bit more formal in order to make this book flexible enough to be used by college students or technicians interested in pursuing formal studies in the field of logic digital. Remember
binary counter count-up built with JK flip-flops. Suppose we have designed a binary counter count-up of 4 bits using four JK flip-flops, which we denote here as a machine. At any time between a pulse of the clock signal and the pulse remains to carry on the counter of a state to the next, we discuss the state of the machine. If at any time between a clock pulse and it is our 4-bit binary counter is the first JK flip-flop in state Q1 = 1, if the second flip-flop is in state Q2 = 0, if the third JK flip-flop is in state Q3 = 0 and if the fourth flip-flop is in state Q4 = 1, then the state of the machine is Q1Q2Q3Q4 = 1001.
Since, by design, this is a machine without inputs, the next state of the machine will Q1Q2Q3Q4 = 1010. Can not be otherwise, since this machine is designed.
Let's look at a representation for a finite state machine (finite state machine) known as state diagram:
Here is a machine that can assume it was constructed with two flip-flops. Each circle represents a state machine, which can only be in a state at any given time. We can see this representation as a game in which the circles are drawn on the ground and at any time are located in one of the circles. According to the diagram, this machine can be in one of three states:
q1q0 = 00 = 01
q1q0 q1q0 = 10
The outer arrows (vertices) to states (circles) leaving or reach a state are the entry or entries placed in the machine at any given time. In this case, we have a machine that has a single entrance designated as x. Let us now see what happens on this machine depending on the value of the input x q = q1q0 state where you are.
If the machine is in the state q1q0 = 00 and the input is x = 1, then the next "clock tick" the machine will go to state q1q0 = 01. But if the input is x = 0 when the machine is in the state, then the next "clock tick" go to state q1q0 = 10.
On the other hand, if the machine is in the state q1q0 = 01 and the input is x = 1, then the following "Clock tick" the machine will go to state q1q0 = 10. But if the input is x = 0 when the machine is in the state q1q0 = 01, then the next "clock tick" the machine will remain in the same state as if it were "stuck" without being able to get out.
Thus, this state diagram completely describes the behavior of the machine for all possible states of the machine.
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