Digital Electronics Basics - Chapter 4: Counters

Publish Date: Mar 27, 2013 | 11 Ratings | 3.55 out of 5 | Print | Submit your review

Overview

The Digital Electronics Basics series present the fundamental theories and concepts taught at entry level electronics courses at both 2 year and 4 year institutions. This series of content provides examples to professors to enable them to easily teach concepts to students, who can develop a solid underlying knowledge of digital electronics using NI solution. This series focuses on some of the basic theory as well as providing the NI Multisim circuits to enable practical implementation and experimentation as homework for students.

Table of Contents

  1. In this Chapter
  2. Example Courses
  3. Counters
  4. Asynchronous Counters
  5. Example Circuit 
  6. Synchronous Counters
  7. Example Circuit
  8. NI Suggested Solution
  9. References

1. In this Chapter

We begin this chapter by studying the two main types of counters and understanding the fundamentals. Then we examine two example circuits which can be used by any educator or student to verify our results using NI Multisim.

If you do not have NI Multisim installed on your computer you can download a free 30 day evaluation at http://www.ni.com/multisim/try/

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2. Example Courses

Listed below are example courses that teach this concept at their schools.

Course Name

School

Learn More

Digital Electronics Basics

Macomb Community College

http://www.macomb.edu/noncms/search/courses/coursekey.asp?coursekey=ELEC-1211

Digital Circuits I

Henry Ford Community College

https://my.hfcc.edu/site_manager/Catalog_Manager/courses/view_course1.asp?id=21589

 

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3. Counters

A counter is a digital sequential logic device that will go through a certain predefined states (for example counting up or down) based on the application of the input pulses. They are utilized in almost all computers and digital electronics systems [1].

There are two main types of counters: Asynchronous and Synchronous counters. We will examine both below and implement them using JK Flip-Flops in NI Multisim.

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4. Asynchronous Counters

This type of counters have JK Flop-Flops arranged in a way that the output of one flip-flip feeds the clock of the following flip-flop [1] as shown in the figure below:

[2]

The output waveforms will result from such a circuit as follows:

[2]

Let us now use NI Multisim to build this circuit and confirm the waveforms above.

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5. Example Circuit 

STEP 1:  Using NI Multisim, open circuit file “async_counter.ms12”. You will notice the circuit below:

STEP 2: Double-click on the Logic Analyzer instrument ‘XLA1’ to open its front panel, then run the simulation. You will notice that the display shows the circuit is indeed counting and the Logic Analyzer shows the results below:

When comparing the results achieved with NI Multisim and the theoretical results, we notice that we confirmed the behaviour of the asynchronous counter with the help of NI Multisim.

Note: The asynchronous counter (also called the ripple counter) is relatively slow due to the fact that each flip-flop’s clock is dependent on the output of the previous flip-flop and because they have a non-zero propagation delay. The synchronous counter eliminates this issue as we will see in the next section [1].

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6. Synchronous Counters

This type of counters has each flip-flop clocked by the same clock source, thus eliminating the cumulative delay found in asynchronous counters [1]:

[3]

Let us now examine this circuits’ behaviour in NI Multisim.

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7. Example Circuit

STEP 3:  Open Circuit file “sync_counter.ms12” using NI Multisim. You will notice the circuit below:

STEP 4: Double-click on the Logic Analyzer instrument ‘XLA1’ to open its front panel, then run the simulation. You will notice that the display shows the circuit is indeed counting and the Logic Analyzer shows the results below:

When comparing the results achieved with NI Multisim and the theoretical results, we notice that we confirmed the behaviour of the synchronous counter with the help of NI Multisim.

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8. NI Suggested Solution

National Instruments offers a number of products that combine to provide a scalable and powerful teaching platform for educators. The solution includes:

NI Multisim circuit teaching environment: Combining an intuitive circuit definition environment, with powerful SPICE simulation technology, educators can use NI Multisim to easily teach the ins-and-outs of circuits in a safe environment.

NI ELVIS teaching and measurement platform allows educators to provide students with a compact, all-in-one unit for their measurement and analysis needs. Combining an oscilloscope, function generator, DMM, bode analyzer and 8 other instruments into a small platform; it simplifies the laboratory experience for students and lab instructors.

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9. References

[1] New Jersey Institute of Technology. ECE394 – Digital Systems Laboratory. Experiment 7: Counters.
[
http://web.njit.edu/~gilhc/ECE394/ECE394-VII.htm]. (14/03/2013)

[2] All About Circuits. Asynchronous counters.
[http://www.allaboutcircuits.com/vol_4/chpt_11/2.html]. (14/03/2013)

[3] All About Circuits. Synchronous counters.
[http://www.allaboutcircuits.com/vol_4/chpt_11/3.html]. (14/03/2013)

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