ABSTRACT
This chapter identifies the parameters and structure of a general sequential circuit. A sequential circuit was basically a combinational logic circuit with feedback, and a range of simple feedback circuits called flip-flops could be devised. The chapter concentrates on the design of logic systems using these discrete building blocks. The output logic can be obtained from the truth table which specifies the outputs for all possible combinations of inputs and internal states. In some sequential circuits there is no need for output logic, as the outputs are identical to the internal states. The feedback applied to the next state logic is crucial to sequential behaviour. The logic outputs that represent the internal state of the system are fed back to provide internal inputs. This enables the next state logic to give different responses to identical external inputs applied to the circuit at different times in a sequence of inputs. The chapter describes the design of sequential logic using discrete flip-flops.
