Digital registers

Introduction

A Flip-flop is a 1 bit memory cell which can be used for storing the digital data. To increase the storage capacity in terms of number of bits, you can use a group of flip-flops. Such a group of flip-flops is known as a Register. The n-bit register will consist of n number of flip-flop(s) and it is capable of storing an n-bit word.

The binary-data, in a register, can be transfered within itself from one flip-flop to another. A shift register is a type of register that allows such data transfers. Shift register has 4 modes of operations.

Shift Registers

A shift register is a piece of circuit that you will find inside a microprocessor. It is used to store and modify data. Now this is one of the simplest explanation I can give for a 2nd grade student.

But if you are some one who is studying about computers, this is just not sufficient. So I will have to explain it in a bit more detail. Alright? I will be getting a bit technical here. But it is how you will get a solid understanding of shift register. So you will have to bare it. Okay?

Sub-modules

The sub-modules of digital registers are:

1. Serial-in Serial-out
2. Serial-in Parallel-out
3. Parallel-in Serial-out
4. Parallel-in Parallel-out

Types Of Shift Registers

Based on the way the data is shifted, we have 5 different types of shift registers. They are:

• Left Shift Registers
• Right Shift Registers
• Bidirectional Shift Registers
• Circular Shift Registers &
• Linear Feedback Shift Registers

Now let explain what each of these registers work like:

Left Shift Registers

We have already talked about the left shift register. So I think you are familiar with it by now. If not, let me re-iterate. So in the case of a left shift register, the data is shifted to the left on each clock cycle.

Right Shift Registers

This is just like the left shift register. But here it is shifting the data to the right on each clock cycle.

Bidirectional Shift Registers

In the case of a bidirectional shift register, we can shift the data in both the directions. So you can shift the data either to it’s left or right!

Circular Shift Registers

In the case of a circular shift register, the last output is connected back as input. So your data will not be thrown out. Instead, will be shifted either left or right in a circular fashion!

Linear Feedback Shift Registers

In this type of shift register, the input of one flip flop will be linear output value of the previous flip flop.

Advantages & Disadvantages Of A Shift Register

It is now time to talk about the advantages & disadvantages of using a shift register. So what are they?

Advantages Of A Shift Register

• They are very fast to use.
• Very quick when you want to convert data from serial to parallel or vice versa. They are faster than normal serial to parallel converter circuits.
• They are very simple in design. So you can easily rig up a circuit to create a shift register.
• We can use them to encrypt or decrypt the data.
• We can use them to a delay signal.
• It is used in CDMA to generate Pseudo Noise Sequence Number.
• We can use them to track our data!

Disadvantages Of A Shift Register

While we could see that it has major advantages, shift register has one major disadvantage. That is:

• The strength of the output current coming from a shift register is not so strong.