Construct a shift register from S-R flip-flops. Explain its working.

Ans:

S-R Flip-Flop Shift Register: Shift registers can be built through using SR flip-flops. Fig.(a) Demonstrates the 4-bit shift register, that uses RS flip-flops. This uses Four SR Flip-Flops in cascade and the inputs to the final three flip-flops in the chain receive complementary inputs, which is if S = 0, R = 1 and if S = 1, R = 0. The first flip-flop has complementary S and R inputs and, thus, this behaves like a D-type flip-flop. Due to the Inverter in the clock line, all data will be transferred to flip-flop outputs upon the positive going edge of the clock pulse.

Now here two inputs A and B. Any one of the inputs can be utilized. Because a 1 input at A or B will be a 1 input at S of the first flip-flop, like a outcome of double complementation, a positive going clock pulse will generate an output of 1 at Q of the first flip-flop. Usually both A and B inputs of the NAND gate are linked together while data is being fed and the NAND is not required to serve as a gate.

Fig.(a) Logic Diagram of S-R Flip-Flop Shift Register