Sequential logic circuit

The characteristic of the sequential logic circuit is that the output signal at any time is not only related to the input signal at that time, and it has to do with the original state of the circuit.

The main steps of the sequential logic circuit reading are as follows :

1. Analyze the circuit composition and write the driving equation to write the driving equation according to the given circuit. An asynchronous sequential circuit also needs to write out the clock equation, and if there is a combinational circuit in the circuit, it needs to write out the output equation.

2. According to the driving equation, the equation of state is written, and the equation of state is replaced by the characteristic equation ( that is, the logical expression ) of the driven equation, and the state equation is obtained.

3. Converting the state equation to a state transition table and a normal truth table, first the values of all states are listed on the left side of the table, then, the substates and corresponding output values of each row are calculated respectively. This method needs to draw the state transition diagram to observe the transformation relationship between states. In solving the substate, we can get the substate more quickly by using the concept of the original variable and the inverse variable.

4. Convert the state transition table to a state transition diagram when using a state transition table without a clock, you need to draw the state transition diagram, in order to observe the transformation between states. When a state transition table with a clock is adopted, the state transition diagram is also recommended, so that the function of the circuit can be analyzed more intuitively.

5. According to the state transition diagram, the function of the circuit is explained according to several state cycles in the state transition diagram to determine whether the circuit can be started. If there is only one state loop, it can be started, and if there is more than one state loop, it can't be started. Indicates whether the number of valid cycles is an incremental counter or a decrement counter, and the mode ( count length ) of the state machine ( counter ) functions, such as decimal number.

This article is from Allicdata Electronics.