- Shift Registers Definition: Shift registers are defined as devices that store and shift bits of input data in sync with clock pulses.
- Data Movement: Data in shift registers can move left or right, determined by clock pulses, allowing for various types of data transmission.
- Buffer Register in Digital Electronics: A buffer register in digital electronics stores data temporarily and allows controlled movement of data bits.
- Circular Shift: By connecting the last flip-flop’s output to the first, data can circulate continuously within the register.
- Types of Shift Registers: There are right-shift and left-shift registers, which determine the direction of data movement within the register.
Shift registers store bits and move them with the clock. Bits may enter or leave in serial or in parallel. Inside the register they move one stage right or left on each pulse.
Figure 1 is a 3-bit chain of rising-edge D flip-flops. The CLR pins of all three flip-flops share one clear input. Q1 of FF1 drives D2 of FF2. Q2 of FF2 drives D3 of FF3. Serial data enters at D1 of FF1 and leaves at Q3 of FF3.
Drive clear high first so every stage is 0. Then present the first input bit B1 at D1.
The first rising clock stores that bit in FF1, so it appears at Q1. At the second clock, B1 is stored in FF2 and appears at Q2 while Q1 holds the next bit B2. At the third rising edge B3 appears at Q1, Q2 = B2 and Q3 = B1.
That left-to-right walk is right-shift transmission. Figure 2 and Table I show the same motion (green arrows) for the input sequence 100100.
Without a wrap-around, the bit in the last flip-flop is lost when a new bit is loaded. Connect FF3 back to the D1 pin of FF1. Then Q3 re-enters FF1 and the word circulates. The middle stages still shift the same way.
A left-shift register moves bits the other way, right to left. Extra gates can control load and read. The stage-to-stage motion stays the same for any register length.
