The following tools are downloaded from various sources on the internet. All the tools are in the shareware or free domain. Please feel free to use them extensively. Most of them have complete documentation and thus should be very easy for beginners.

LOGICSIM:

Author: Arnoud Masson

File Size: 357K; Platform: Macintosh; Type: .sit; Version: 3.0b

Drawing a schematic is a lot like programming, only instead of knowing almost instantly if your design will work, you have to solder all the circuits to the board and then push a charge through them. This program saves engineers from the tedious task of building real boards only to find they don't work. LogicSim is a virtual circuit board onto which you can add and connect various types of circuits, and then test them to see if they work; and if they don't, you can easily identify where the problem is and make changes where necessary. The interface consists of a scrolling list of icons representing different circuits on the left and the drawing board (also in a scrolling window) on the right. Adding circuits is as simple as dragging and dropping, and then Option-clicking and dragging pins to connect them. Testing the circuit (class) is as simple as choosing \Simulation\ from the \Circuit\ pull-down menu. Any unconnect pins will cause an error and the unconnected pins will be selected. The simulation mode also shows the binary value of the inputs and the outputs from each circuit. That way, if you don't get the results you expected, you can analyze their progress by following their paths, checking their values along the way. LogicSim supports the importing and exporting of groups of circuits as classes. Thus, once you create a clock, for example, you can include that clock in any other circuit simply by importing it as a circuit class. Although the design is simple, not all the standard Macintosh drawing functions are supported. Some of those functions include: Shift-clicking to multiple select, resizing by dragging a corner handle, and a few more. Also, there is no support for the uninformed. A basic knowledge of electrical engineering is a prerequisite for being productive with this program and advanced studies in the field would prove extremely helpful. Nevertheless, these few lacking features should not detract from the truly powerful concept behind this program and anyone interested in learning could go a long way with an introductory textbook and this program.

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DIGISIM:

Author: Brian Rauchfuss

File Size: 51K; Platform: Macintosh; Type: .sit; Version: 2.8

DigSim is a program for designing and experimenting with digital circuits. It is useful for both learning digital logic and for testing advanced circuit ideas. When DigSim starts up, a palette of circuit elements and an untitled circuit window appear. You simply drag any of the elements over to a circuit window to add them to the circuit. Once the circuit is complete, you can actually run it to see if it would really work. DigSim is obviously fairly esoteric, but it's a good simulation of digital circuitry and bound to be of value to people interested in the subject.

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xLOGIC CIRCUITS:

Author: David Eck

File Size: 82K; Platform: Macintosh; Type: .sit; Version: 1.2

This utility, by the author of the excellent math plotting program \xFunctions,\ is a simple virtual circuit board on which you can build and test logic circuits using five tools: AND, OR and NOT gates, a power source (which is continually on) and a variable delay switch. In addition, externally created circuits can be included as subcircuits, allowing much more complex formations than would normally fit on the \board.\ Electrical flow is shown with solid lines, while \dead\ wires are displayed as dotted lines. Eight input and eight output leads indicate whether the result of the power flow is on or off. There are some notable drawbacks, the most significant being that once elements are placed on the board, they cannot be removed (unless you press \Undo\ immediately after it's placed). This makes xLogicCircuits unsuitable for tinkering; however, such a lack makes it perfect for testing electronics and logic students on already-acquired knowledge. And being forced to get it right the first time instills discipline in the logic world, a field which is becoming ever more complex as the computer field does.

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DIGITAL LOGIC ANALYZER:

Author: Xidicone Pty. Ltd

File Size: 700K; Platform: IBM; Type: .zip; Version: 1.0

Digital Logic Analyzer turns your PC into a hardware logic analyzer which can be used to analyze and debug electronic circuits. The program offers a maximum internal sample rate of 6 MHz and an external sample rate greater than 10 MHz. Over-voltage protection is provided on all input channels.

Download Digital Logic Analyzer