ABSTRACT
Latches and flip-flops are the basic building blocks of most sequential circuits. An unclocked latch is a sequential device that can change its output at any time, whereas a clocked latch and a flip-flop can only change their outputs after an appropriate clock signal occurs. The state diagram provides a graphical representation of the characteristics of the latch by showing the possible transitions and is another method of displaying the same information. Most digital systems operate in a synchronous mode, under the control of a master clock signal. The master clock generates a train of periodic pulses which are distributed throughout the system, allowing data to flow in a predetermined manner rather than a ripple through the system. The clock input is also called a control input since it controls the response from the latch. There are three major categories of the flip-flop: the pulse-triggered master/slave, the edge-triggered, and the data-lockout flip-flop.
