Shift Registers – Types , Applications

Shift Registers – Types , Applications
Shift Registers – Types , Applications

Shift Registers  Flip-flops are capable of storing a single binary bit (1 or 0). However, in order to store multiple pieces of data, a quantity of flip flops is required. Given that a single flip flop is capable of storing a single bit of information, n flip flops are connected to store n bits of data. Information is stored in a register, which is a device utilized in digital electronics.Flip-flops are utilized in the register construction process. A register consists of a collection of flip-flops that are employed to store multiple pieces of data. To store 16-bit data, for instance, a computer requires a set of 16 flip-flops. Depending on the need, the inputs and outputs of a register may be serial or parallel.

The sequence of data bits that are stored in registers is referred to as a “word” or “byte,” with a “byte” comprising eight bits and a “word” comprising sixteen bits (or two bytes).The arrangement of several flip-flops connected in series is referred to as a register. Information that is stored may be transmitted between registers; such registers are referred to as “Shift Registers.” A shift register is a sequential circuit that, with each clock cycle, stores data and advances it towards the output.

Basically shift registers are of 4 types. They are

  • Serial In Serial Out shift register
  • Serial In parallel Out shift register
  • Parallel In Serial Out shift register
  • Parallel In parallel Out shift register

Serial in Serial Out Shift Register

The register receives its input in a sequential fashion, wherein each bit is inputted via a solitary data line. In a similar fashion, the output is collected serially. It is not feasible to shift the data in an exclusively left or right direction. Consequently, this device is commonly denoted as a SISO shift register or a Serial in Serial out shift register.

Incoming data is converted bit-by-bit from the right to the left by the shift register. Four-bit SISO shift registers consist of four flip-flops and three connections.

  • The term “shift left registers” refers to the registers utilized to transfer bits to the left.
  • The term “shift right registers” denotes the registers responsible for executing rightward bit movements.
  • For instance, entering the values 1101 into the data input will cause the output to be shifted by 0110.

Among the four varieties, this register is the most basic. The serial data is connected to the flip-flop positioned to the left or right, given that the clock signal is connected to all four flip-flops. Following this, the input of the subsequent flip-flop is connected to the output of the initial flip-flop. At the farmost flip-flop, the shift register’s ultimate output is accumulated.

When the clock signal is applied and the serial data is supplied, this shift register will only output one bit at a time in the sequence of the input data. SISO shift registers are utilized as transient data storage devices. However, its primary function is to function as a delay element.

Serial in Parallel Out shift register

In this register, serial input is provided, whereas parallel output is accumulated.To recalibrate all four flip-flops, the clear (CLR) signal is connected in conjunction with the clock signal. The direction of serial data connected to one end of each flip-flop is specified by specifying whether the shift is to the left or right register. Subsequently, the output of the initial flip-flop is connected to the input of the subsequent flip-flop. A synchronized timepiece is attached to every individual flip-flop.

Serial in Parallel Out (SIPO) shift registers compound the output of each flip-flop, as opposed to serial in serial out (SIPO) shift registers. The respective outputs of the first, second, third, and fourth flip-flops are represented by the letters Q1, Q2, Q3, and Q4.The primary function of the Serial to Parallel Output Shift Register is to convert serial data to parallel data. Consequently, they are utilized in communication lines where the demultiplexing of a solitary data line into numerous parallel lines is required.

Parallel in Serial out shift register

The register operates in parallel to receive input, resulting in the individual supply of data to each flip-flop. Subsequently, the output is gathered in serial at the terminal flip-flop.

Although the clock input is directly connected to each flip-flop, the input data is multiplicatively divided by one through the use of a mux (multiplexer) at the input of each flip-flop. D1, D2, D3, and D4 denote, correspondingly, the parallel inputs to the shift register. In this register, the serial collection of the output takes place.

The parallel data input and the output of the previous flip-flop are connected to the input of the MUX, whereas the output of the MUX is linked to the subsequent flip-flop. A shift register that operates in parallel to serial is known as a Parallel in Serial Out (PISO) register. Consequently, they are utilized in communication lines where a single serial data line multiplexes multiple data lines.

Parallel in Parallel out shift register

The input is concurrently supplied and the output is concurrently collected in this register. The four flip-flops are each connected to a clock and clear (CLR) signal. Each flip-flop receives input data on an individual basis, and each flip-flop contributes output data alone.

A Parallel in Parallel out (PIPO) shift register serves as a delay element and transient storage device, similar to a SISO shift register.

Ring Counter

The idea is to set up a feedback loop by feeding the output of one flip-flop into the input of another, and so on, until the last flip-flop is fed into the first one. A “Ring Counter” is the term used to describe this.The logic 1 high input of the first flip-flop is connected to the input of the second, and so on in a precise order.The final step is to re-insert the first flip-flop’s output into the last one. First clock pulse applies a 1 to the arrangement’s second stage input and a 0 to the other inputs. Input 1 is flipped in this way around the ring.

Other Type of Registers

Bidirectional Shift Register

A binary number is shifted to the left by one point when multiplied by 2. Similarly, shifting the position of a binary integer one to the right is equivalent to dividing it by 2.Therefore, for some mathematical processes, a shift register—which may change the bits in either direction—is required. One such tool for this task is the Bidirectional Shift Register.

There is only one possible direction for data to be shifted by any of the previously stated shift registers; that is, to the right or the left.A bidirectional shift register can be described as “the register in which the data can be shifted either left of right.”. A clock signal, an input/output serial data line, and a mode input that can be configured to right or left shift are all included with this register.The mode input allows you to control the left and right shifts. A high mode input value (1) will be shown to the right of the data. By the same token, a low mode input will cause a leftward shift in the data (0).

The circuit of a bidirectional shift register using D flip flops is shown below.

Bidirectional shift register

Universal Shift Register

An example of a universal shift register would be one that can take in data in parallel and then shift it to the left or right.

The three operations that this register can do are detailed below.

  • Parallel loading
  • Taking a left turn
  • Riding to the side.

This means that data can be stored and transmitted simultaneously using the universal shift register. Utilizing shift left and shift right operations on a serial route enables data storage and communication in a similar manner.

Depending on our needs, the universal shift register can accept serial or parallel data and return it in the same manner. “Universal Shift Register” and similar commands are suitable because it can perform shifts in four directions: left to right, right to left, serial to parallel, and serial to parallel.

Applications of Shift Registers

A register is an essential component of any digital electrical device, including computers, because

  • Quickly store information
  • Data transfer
  • Updating information
  • Against which they stand.

Computers store information via shift registers. Digital systems rely on data storage components such as random access memory (RAM) and other types of registers to efficiently store the enormous volumes of data.

In digital systems, operations like division and multiplication are performed by means of registers. To transfer data, a variety of serial shift registers are employed.

Some examples of devices that rely on counters are digital clocks, frequency counters, and binary counters.

  • Using serial in-serial out registers, time delays can be introduced.
  • The usage of serial in-parallel out registers allows for the conversion of data formats, from serial to parallel.
  • “Serial to parallel converters” is still another way of describing them.
  • Using a parallel in- serial out register, data that is in parallel form can be transformed to serial form. “Parallel to serial converters” is thus another suitable term for them.

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