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Co Simulation Of Vhdl And Spice – Teaching The Whole Picture In Digital Design Labs

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2005 Annual Conference


Portland, Oregon

Publication Date

June 12, 2005

Start Date

June 12, 2005

End Date

June 15, 2005



Conference Session

Lab Experiments & Other Initiatives

Page Count


Page Numbers

10.312.1 - 10.312.8

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Paper Authors

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Shauna Rae

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

Co-simulation of VHDL and SPICE – Teaching the Whole Picture in Digital Design Labs

Shauna L. Rae Electronics Workbench

Abstract – The use of hardware description languages is now an essential part of digital design. As a result, professors require new and innovative ways to deliver course content that teaches both hardware description languages and digital design. Co-simulation of VHDL with other electronic devices allows students to place their VHDL-based components into a circuit with other types of devices such as switches, LEDs, seven-segment displays and other drivers. It provides students with the electronics context that waveform-based simulations fail to provide. We will examine how to incorporate co-simulation of VHDL and SPICE-modeled components into existing digital design curriculum.


The methods used to implement and design digital logic into practical circuits have changed dramatically over the last ten years. FPGAs and CPLDs have replaced much of the glue logic used in the past and have allowed more and more complicated designs to be placed on a single chip. These increasingly complicated designs have made gate-based design impractical, causing Hardware Description Languages (HDLs) such as VHDL to replace traditional design methodologies. Over the past decade, instructors have converted introductory and advanced digital design curriculum to include teaching design in conjunction with hardware description languages such as VHDL1, 4, 7, 8, 10, 13. Many digital design textbooks have also evolved to include hardware description language examples 2, 6, 9, 12.

The problem arises that VHDL can seem removed from electronics. When students are working in a programming and waveform-only simulation environment, they may lose sight of the context in which the VHDL code is ultimately used. They may also have limited access to labs that would enable them to program their code onto target devices and verify the operation in a real circuit.

Co-simulation of VHDL and SPICE enables instructors to provide students with a simulation environment that resembles a real circuit and helps them to reinforce concepts that go unnoticed in the traditional waveform simulations that usually accompany HDL designs. Students can connect input switches, LEDs and seven-segment displays to their VHDL-based components. This helps them gain context and learn about design elements such as when to use pull-up resistors and the importance of converting hexadecimal numbers to the more readable decimal system. As students progress, they can connect VHDL-based components to more complicated circuitry such as relays, MOSFET drivers, and analog to digital converters. Since these components have SPICE models, the advanced student can simulate an entire design or project.

Proceedings of the 2005 American Society for Engineering Education Annual Conference & Exposition Copyright © 2005, American Society for Engineering Education

Rae, S. (2005, June), Co Simulation Of Vhdl And Spice – Teaching The Whole Picture In Digital Design Labs Paper presented at 2005 Annual Conference, Portland, Oregon.

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