Digital Counter

A Digital Counter is obtained by arranging the flip-flops. These are the applications of flip-flops. Other than counting, these are used for measuring the frequency as well as time. These are used to increase the addresses in memory. The operation of these devices depends on the single clock applied.  These are made of flip-fops as basic elements. There are two states included in the flip-flops. The high state is represented by 1 and the low state by 0. The operation of the counter can be made possible by high state-driven flip-flops. Counters consist of modes that are represented by the number of countable states, for example a mod-8 counter. In this, the number of states countable is from 000 to 111 (that is 0 to 7). Hence eight countable states name the counter as a mod-8 counter.

What is Digital Counter?

Definition: The circuit is designed with digital logic to obtain information about the number of events that occurred. This type of digital logic device can be defined as a Counter. The design of counters can be achieved by following various steps.

1. The number of Flip-Flops based on the requirement.
2. Accordingly, the State diagrams/ Excitation Tables are drawn.
3. Further, the expressions are minimized using various techniques.
4. Finally, the logic diagram is designed.

The above steps are especially followed fro the design of the type of counter known as Synchronous Counters.

Types of Digital Counters

The interconnection of the flip-flops results in the classification of the counters.  Although the single clock signal applied to the counters. There is a difference among the operation based on a single cock applied to the flip-flops in the circuit or the signal applied to the main flip-flop.

The types of counters are:

1. Asynchronous Counters
2. Synchronous Counters

The asynchronous counters are also referred to as Ripple counters. The simplest in design among the other counters is the ripple counter. The least quantity of hardware is required for this counter. The flip of one stage reflects the flip in another stage in asynchronous counters. These counters are further described as ‘Serial Counters’.

But in the other type of counter called synchronous counters, each flip-flop in the circuit gets triggered with the same clock at the same time. This is possible by connecting each flip-flop clock line with a single clock. The operation occurred in such types of circuits will be in coordination or synchronization with all the flip-flops present.  Hence these are referred to as Synchronous Counters.

Based on the clock signal applied the counters are classified as synchronous and asynchronous counters. In the Asynchronous type, only the first flip-flop is provided by the main cock. the remaining flip-flops are powered with the output obtained in the previous stage of flip-flops. There is another category of counters referred to as Decade Counters. This counter is able to count the pulses for ten values. The counting is done from 0 to 9.  Even this counting can be extended to 15 states.

What is the difference between Synchronous and Asynchronous Counters?

Based on the connections and the clock applied to the flip-flops there are certain differences between Synchronous and Asynchronous counters.  Some of the differences are listed as follows:

 

Asynchronous Counters	Synchronous Counters
1. In this counter, the main clock is applied to the first flip-flop. Whereas the other flip-flops are provided with the clock from the output of previous stage flip-flops.	1. The arrangement of the flip-flops in this counter is driven by the same clock.
2. The clock is not simultaneous for all the flip-flops in the circuit.	2. The clock is simultaneously provided for all the flip-fops.
3. To the more number of states, the design of this counter is simple to implement.	3. In this counter, as the number of states is increasing the design tends to become complex.
4. The propagation delay is more as the counters are not in sync.	4. The propagation delay will be less in comparison to the asynchronous counters because of the sync among the flip-flops.

In comparison to the asynchronous counters, the operation will be fast in synchronous counters. The frequency required for operation in the synchronous counters is high. In terms of cost, it is low in asynchronous counters.

Digital Counter Applications

These counter circuits are the basic ones in the ‘Digital Electronics’. These counters possess various applications.

1. In the conversions from Analog to Digital, these counters are used.
2.   In the applications of Timers for example Washings machines where we set the time. These counters are used.
3. With the help of these counters, a ‘Digital Triangular Wave Generator’ can be designed.
4. In the application of ‘Digital Clock’ counters are used.
5. A practical example of these devices is seen in the malls, stadiums, or the auditoriums. In the above situations to keep the data on the number of persons. This can be made possible or it will become simple because of these counters.

 

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.