This obsolete application is reminiscent of the acoustic mercury delay lines used as early computer memory. The stages in a shift register are delay stages, typically type 'D' Flip-Flops or type 'JK' Flip-flops.įormerly, very long (several hundred stages) shift registers served as digital memory. Thus, a four stage shift register delays 'data in' by four clocks to 'data out'. A waveform synchronized to a clock, a repeating square wave, is delayed by 'n' discrete clock times, where 'n' is the number of shift register stages. Shift registers produce a discrete delay of a digital signal or waveform. In other words, sequential logic remembers past events. Sequential logic, unlike combinational logic is not only affected by the present inputs, but also, by the prior history. Shift registers, like counters, are a form of sequential logic. Parallel-in/ parallel-out and universal devices.Parallel-in, parallel-out, universal shift register.Lessons In Electric Circuits - Volume IV Chapter 12 SHIFT REGISTERS Lessons In Electric Circuits - Volume IV (Digital) - Chapter 12