Digital Logic Systems

David N. Warren-Smith, CPEng. South Australia

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Mission statement

To design digital circuitry and equipment in a professional and effective way and to promote the  use of logical design techniques in the design of digital circuitry.

Disclaimer - Any views expressed in these pages are my own and not necessarily those of any organisation that I am associated with.

Welcome to my digital world

TopAlign heading with top of screenWhat can you find on this web site?

This web site is intended to be of interest to digital circuit designers and students of digital circuit design. I have included a range of topics from an article for the celebrated bystander in the street to something I hope will be of interest to the serious designer, whether student or professional. The articles button on the panel will take you to an introduction to all the articles. There are a few links to miscellaneous non technical pages in the panel on the left.

The articles that you can read on this site are arranged in roughly three groups. There are tutorial articles on Boolean algebra, including the article for the casual bystander, practical project oriented articles and articles with a more theoretical content. You can go directly to any of the three streams of articles through the buttons on the left of the screen.

You can read an introductory article on Boolean Algebra. This article is intended to provide the background required for the remaining articles. One omission from this articles is a discussion of binary numbers. Most beginning books on digital design give the necessary explanation of number systems. The Boolean algebra article became too long for a single page and I have split it over two pages. You can go directly to the Boolean Algebra Page 1.

A natural progression of ideas after establishing the concept of Boolean algebra is to consider what happens when feedback is applied within a combinatorial circuit.  The page on asynchronous logic demonstrates that memory is created in the circuit. The combination of logic and memory allows the circuit to make decisions and determine its response to a sequence of external events. This is the beginning of intelligence and automation in a machine. You can go directly to the Intelligent Logic page.

If exclusive-OR logic is new to you you should read the Boolean algebra pages first to discover that Boolean algebra actually consists of at least three complete algebras two of which are described in some detail for the design of digital circuits. The third complete algebra is described briefly. These are termed the inclusive-OR and the exclusive-OR algebras. Someone asked my why would you need exclusive-OR algebra? Good question, why would you leave out a significant part of the subject?

TopAlign heading with top of screenBuy a Book or Project PC Board?

There are two items that you can buy from this web site:

1. If you are an electronics enthusiast you can buy one of my project boards. These boards are especially designed for students, enthusiasts or even beginning digital engineers. Follow this link to see how you can create projects quickly with one of these project boards. I have very few of these boards left so you might be out of luck, unless you want a substantial number of them. Check out my project board

2. Buy the second edition of the book entitled: "Introduction to Digital Circuit Theory" (ISBN: 978-0-9581894-1-5). The book is in the form of a monograph with comb binding, card back and clear cover in A4 format. The current revision includes a number of inadvertent error corrections. The single copy price is $39.95 (Australian dollars), which includes all currency fees and airmail charges if purchased with the Buy Now button. PayPal will carry out the conversion of your currency to Australian currency in a secure transaction and e-mail me your order. Please follow this link Purchasing information if you would prefer alternative arrangements to purchasing the book:

Purchase the book securely through PayPal:

TopAlign heading with top of screenWhat is Programmable Logic?

Programmable logic is a system for encapsulating your digital circuitry into a programmable integrated circuit device without you having to leave your PC.

The Altera system offers a comprehensive and powerful integrated windows based development environment, which includes editors (graphical and text), simulators (full timing and functional analysis), a compiler and all required support facilities such as programming software and error message windows. The Altera system supports a large range of fully reprogrammable devices and device styles including in-system programmable devices from small (300 useable gates) up to very large devices (1,000,000 and more useable gates).

Xilinx Inc. are an alternative source of programmable logic devices with much the same capabilities as the Altera devices. However, their CoolRunner range of low power consumption devices are unmatched for portable applications. (CoolRunner is a trade mark of Xilinx Inc.)

TopAlign heading with top of screenTake a course

If you live in South Australia and are contemplating studying electronics you can take a course in Digital Circuit Design, including theory and hands on practice with programmable logic devices, at either Regency Institute of TAFE or Torrens Valley Institute of TAFE, both in South Australia. Go to the links page to visit either of these sites.

TopAlign heading with top of screenAny questions or comments?

If you have any questions on the subject of any of the papers or would like to comment on them you can contact me through my e-mail link shown below.

If you have a web site similar to this one, let me know the URL and I will add it to my links page or one of my other pages. I am happy to talk to fellow enthusiasts.

Some of the comments and sometimes critical comments that I have received have been very helpful in enabling me to improve my material. Many thanks to the people that have communicated with me.

Press buttons for: Links OR Top of the page OR Articles page:

David N. Warren-Smith, CPEng

PO Box 647, Elizabeth, South Australia 5112

Last edited: 22 November 2009