Design of a microcomputer software breadboard for digital logic circuits
Mutuku, Joseph Ndisya
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A simulation package for digital logic circuits helps a designer to build and simulate the devices and their interconnections to form a logic circuit. It also allows the substitution of the components, change of inputs and control parameters, while observing their effects on the outputs at various circuit test points. The circuit configuration can be stored on a computer file for future editing and application. Simulation packages are expensive and not available to the local undergraduate users and are limited to institutions and circuit designers we can afford to buy them. There is therefore a need for the development of a cost-effective simulation package capable of modeling the common logic devices used in undergraduate syllabus. This project highlights the issues in the design of a Software Breadboard (SBB) package for simulating the digital logic circuits. In this project, a model of digital circuits is constructed using the devices as building blocks with their interconnections. It also shows the signal propagation through the different devices. A program structure, based on this model, is developed using the Jackson Structured Programming (JSP) technique. The structure is finally transformed into GW-BASIC running on an IBM PC model 30 or a compatible microcomputer. The package is capable of modeling the functional behaviour of the device parameters in a circuit, that is, device specifications and their terminal interconnections including their input values. The program is interactive and user-friendly and hence guides the user through all the stages of the program run. The program is used ot simulate several logic circuits and the results obtained are found to be in agreement with the theoretical values.