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BY MEL BECKMAN

For years Electrical Engineering students have learned to design digital circuits containing integrated circuit chips using a homely little device called an IC breadboard trainer. The typical trainer consists of a white plastic block containing hundreds of socketed holes; a power supply; and a few ancillary switches, indicator lamps, and buzzers mounted around the periphery of the block. Students plug chips into the holes, and then plug wires into other holes to connect the pins of the chips to other chips on the breadboard or to the peripheral switches and whatnot. Then the student throws the on switch and is rewarded with wither expected results or a burned out chip.

MacBreadboard simulates every aspect of these trainers. It displays, with uncanny fidelity, a full-color, three-dimensional replica, complete with power supply, assorted switches, LEDs, seven-segment readouts, a buzzer, and a variable-speed clock. You use the mouse to install chips from a library of 78 standard parts, dragging to make connections with wires. On a color Mac, wires of different lengths appear in different colors as they do on real breadboards. You can turn on the juice at any time to see your circuit operate. The mouse pointer doubles as a logic probe, letting you test any circuit connection for voltage.

Circuit using the optional clock, which simply generates consecutive digital pulses at a rate you select, can display a timing diagram plotting state changes for all of the switches and indicators. Such diagrams are an indispensable tool for understanding circuit operation, and they have to be drawn by hand when using real breadboards. To help with debugging, MacBreadboard's Step mode lets you advance the clock one pulse at a time as you watch the circuit operate.

The board is large enough to accommodate five or six chips (depending on the number of pins) so you can build complex circuits. However, I was frustrated that I couldn't expand the working area when I wanted to add “just one more chip.”

MacBreadboard's manual lacks an index but is otherwise complete including an appendix with detailed schematics for each of the available chips. Very good online help covers the same material as the manual, including schematics of the chip library. Unfortunately, you can't augment the library with more chip types. You're stuck with the ones YOERIC supplies: a selection of gate, inverter, shift register, arithmetic, and counter ICs commonly used for introductory courses, but no advanced devices such as memory or microprocessors.

In spite of some limitations, MacBreadboard is a useful educational device that accurately replicates and even surpasses the behavior of the physical tool it simulates. Except, of course, for the toasted chips.

 

BY DAVID BELLIN

MacBreadboard is an excellent example of what a local company can do with imagination and an interest in the educational software market. YOERIC created MacBreadboard to fill the needs of undergraduate digital design courses and they have done an excellent job.

With the cutbacks in higher education all schools are experiencing, students are having a difficult time getting “hands on” experience in basic engineering courses. After all, digital logic chips, solder, wires, and the “breadboards” used to wire up circuits cost money. At the same time, these basic circuits are not very complex, and the same basic designs are repeated every semester by different students. This kind of teaching is perfect for use of the graphic Macintosh interface to present the equivalent of hardware digital logic trainers, using TTL chips as the basic components to be “wired” together using software. I found the program logical, easy to use, accurate. My only suggestions would be the inclusion of a larger set of TTL's (only 78 are currently supplied). However, the inclusion of simulated buzzers, dips, and a logic probe are all welcome. If all these terms are familiar to you, and you'd like to brush up on your fundamentals, MacBreadboard is the tool you want to try!

MacBreaboard is a unique simulation program which allows electronic students to manipulate chips and wires to construct digital circuits on the computer screen rather than on a real “breadboard” with power supply. This innovative simulation works like a real breadboard but does not require the purchase of the breadboard, power supply or electronic parts (chips, transistors, or wires), the cost of which would quickly add up to well over the cost of the software.

The program features more then 75 chips from which to choose. Immediate feedback is given to the user, who can design a project, test it, and then modify it based on the results displayed on MacBreadboard. This is an excellent tool for teaching digital electronics to high school through adult physics/electronics classes before students actually go into the lab.