Table of Contents
Joop Liedorp
Technical University Delft
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The application VHDLEDIT/VHDLSIM allows the creation and simulation in pseudo real time of digital circuits. It uses a small subset of the hardware description language VHDL to describe the circuits. Pulse generators are available to provide continuous input stimuli to the circuits and stripchart recorders and number displays to show results. The status of the ports is also shown in the circuit.
The application allows the creation and simulation of a lot of (basic) digital circuits. One can think of - adders - multipliers - shift registers - memory cells - combinatorial circuits The behaviour of these circuits is shown in pseudo real time.
The standard approach to cover the teaching of the topics mentioned above is done with textbooks. The application can be an important addition to this, because the students now can see how the circuits do behave and what its difficulties are.
The application consists of two parts: an editor to generate the basic building blocks that can be used to form circuits, and the simulator. Here these circuits, connected to each other, to the generators and displays can be simulated. Both programs are developed under Xwindows and Motif. In the edit part, the user is guided to make circuit descriptions using the mouse and Motif push buttons and the keyboard. The (basic) circuits made can be saved to files for use within the simulations. In the simulator part of the application these (basic) circuits can be placed in a work area and connected to each other by mouse input. Puls generators and displays also can be placed and connected this way. Input stimuli can come from the puls generators, or they can be given by clicking the mouse on an input port of which the status must be changed. A settable time scale is added, so the speed at which the simulation is carried out can be changed.
This application can be used in two ways:
a. In classes in which the teacher can show circuits and comment on the important events that occur during the simulation.
b. In laboratories by students to build circuits of their own and investigate their behaviour.
The program is still in a more or less experimental stage. It will be evaluated during a vhdl_vlsi design course for third year students at the T U Delft.