Shift Register Introduction

Shift Registers are sequential logic circuits, capable of storage and transfer of data. They are made up of Flip Flops which are connected in such a way that the output of one flip flop could serve as the input of the other flip-flop, depending on the type of shift registers being created.

Shift registers are basically a type of register which have the ability to transfer (“shift”) data. Registers are generically storage devices which are created by connecting a specific number of flip flops together in series and the amount of data (number of bits) which can be stored by the register is always directly proportional to the number of flip flops, as each flip flop is capable of storing only one bit at a time. When the flip-flops in a register are connected in such a way that the output of one flip flop, becomes the input of the other, a shift register is created.

Most commonly used in the creation of shift registers are the D (Delay)-flip flops.

For the operation of the D flip flops which makes them so desirable for shift registers, Whenever there is a change on the clock of a D flip flop (either rising or falling edge, depending on the specifications of the flip flop). The data at the output “Q” becomes the same data as the one at the input “D”. The Output “Q” of the flip flop will stay at that value until the next clock cycle, where it will then change again to the value(High or low, 1 or 0) at the input.