ABSTRACT
This chapter uses a simple sequential circuit with a single feedback connection as a prototype from which a range of flip-flops will be developed. The flip-flops can be regarded as the building block of a discrete sequential logic system. A sequential logic circuit, in its simplest form, is a combinational logic system with some feedback connections from the output, providing one or more additional internal inputs. Data is applied to the external inputs, but the user has no direct control over the internal inputs. They can only be changed by the logic circuit itself responding to all its inputs, both external and internal. The value of the internal inputs defines the state of the system. The set-reset flip-flop (SRFF) is a simple sequential circuit having only one feedback loop. Flip-flops can be regarded as the elementary building blocks of sequential systems.
