Question

3 Theory A shift register is a series of flip-flops connected so that data can be transferred to a neighbor each time the clock pulse is active. An example is the display on your calculator. As numbers are entered on the keypad, the previously entered numbers are shifted to the left. Shift registers can be made to shift data to the left, to the right, or in either direction (bi-directional), using a control signal. They can be made from either D or J-K flip-flops. An example of a simple shift register made from D flip-flops is shown in (a) below. The data is entered serially at the left and may be removed in either parallel or serial fashion. With some additional logic, the data may also be entered in parallel, as shown in (b) below Shift registers are available in IC form with various bit lengths, loading methods, and shift directions. They are widely used to change data from serial form to parallel form, and vice-versa. Other applications for shift registers include arithmetic operations in computers Another application of the shift register is as a digital waveform generator. Generally, a waveform generator requires feedback - that is, the output of the register is returned to the input and recirculated Two important waveform generators are the Johnson (or "twisted- ring") counter and the ring counter. The names are easily associated with the correct circuit if the circuits are drawn in the manner shown in (a) and (b) below a) Ring counter