Counters & Shift Registers

A Shift register is a cascade of flip flops, sharing the same clock, in which the output of each flip-flop is connected to the data input of the next flip-flop in the chain, resulting in a circuit that shifts by one position the bit array stored in it. This shifts the data present at its input and shifts out the last bit in the array at each transition of the clock input. A counter is used to count the events happening in a system. The most common of these are called Johnson counters and ring counters. Because the data changes in response to a clocking signal, they are used to determine the different time or state.