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Computer Circuit Lab Experiments Using Limited Lab Resources

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2001 Annual Conference


Albuquerque, New Mexico

Publication Date

June 24, 2001

Start Date

June 24, 2001

End Date

June 27, 2001



Page Count


Page Numbers

6.287.1 - 6.287.6

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Paper Authors

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Christopher Carroll

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NOTE: The first page of text has been automatically extracted and included below in lieu of an abstract

Session 1520

Computer Circuit Lab Experiments Using Limited Lab Resources Christopher R. Carroll University of Minnesota Duluth


Lab experiments in which students design and test functional parts of digital computers are useful endeavors that demonstrate how computer functions can be implemented and that reduce the mystery that surrounds computer circuits in students’ minds. However, generating lab assignments that both involve significant processing functions and require manageable amounts of hardware is a daunting task for course instructors. Many educators have turned to simulation of digital circuits that implement computer functions, a decision that removes the student from the actual hands-on contact with circuits and components that are involved in computer design. There is no better way to gain a gut feeling for how a circuit functions than to build it and make it work, including understanding the curious circuit behaviors that can result from misplaced wires or faulty components. Simulation separates the student from the operation of the circuit, and can increase the student’s perception that the circuit is “too complicated” or “too mysterious” to implement on a breadboard.

Often the most cumbersome part of a computer circuit implementation is providing input and output interfacing. The author developed a simple microcontroller-based instrument that implements a 12-key keypad input and a 16-character hexadecimal display for use in interfacing digital circuits, which was reported at an earlier ASEE conference1. This paper reveals several lab experiments that have been performed by students to investigate digital computer functions, including arithmetic circuits such as multipliers and dividers and data structure implementations such as queues (FIFOs) and stacks (LIFOs). These lab experiments all have been completed by students using just a handful of standard logic chips plus the author’s input/output instrument mentioned above. By breadboarding these circuits, rather than simulating them, students obtain a fuller understanding of how the circuits work and gain confidence in the design of computer systems.

Carroll’s Gadget

The instrument that makes developing manageable computer circuit lab exercises easy is known as Carroll’s Gadget. Its design was reported in an earlier ASEE conference paper1. This instrument, designed and built by the author, is housed in an old telephone handset and consists of a microcontroller-based circuit that uses the 12-key telephone keypad as an input devices and that generates a display of up to sixteen hexadecimal characters on a standard oscilloscope screen for use as an output device. The instrument

Proceedings of the 2001 American Society for Engineering Education Annual Conference & Exposition Copyright 2001, American Society for Engineering Education

Carroll, C. (2001, June), Computer Circuit Lab Experiments Using Limited Lab Resources Paper presented at 2001 Annual Conference, Albuquerque, New Mexico.

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