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Unformatted text preview: 6.004 Computation Structures - 1 - JSim M A S S A C H U S E T T S I N S T I T U T E O F T E C H N O L O G Y DEPARTMENT OF ELECTRICAL ENGINEERING AND COMPUTER SCIENCE 6.004 Computation Structures JSim Contents: 1. Introduction to JSim 2. Running JSim 3. Netlist format 4. Device statements 5. User-defined subcircuits 6. Built-in subcircuits 7. Control statements 8. Running a simulation 9. Waveform browsing 1. Introduction to JSim JSim is a computer-aided design (CAD) tool that provides: • A simple editor for entering a circuit description (called a “netlist”) • A choice of programs to simulate your circuit • A waveform browser to view the results of a simulation JSim uses mathematical models of circuit elements to make predictions of how a circuit will behave both statically (DC analysis) and dynamically (transient analysis). The model for each circuit element is parameterized, with each parameter providing information about the design or physical properties of the device. You’ll specify the design parameters in your netlist, e.g., for a mosfet you would specify its length and width. The parameters specifying physical properties have been derived from measurements taken at the integrated circuit fabrication facility. We’ll provide those parameters as part of the mosfet model. 6.004 Computation Structures - 2 - JSim 2. Running JSim Running on Athena We recommend using the computers in the 6.004 lab (34-501) since JSim has been tested and is known to run with satisfactory performance in that environment. Another benefit of using the 6.004 lab is that there’s plenty of help around, both from your fellow students and the course staff. After signing onto the Athena station, add the 6.004 locker to gain access to the design tools and model files (you only have to do this once each session): athena% add 6.004 Start JSim running in a separate window by typing athena% jsim & It can take a few moments for the Java runtime system to start up, please be patient! JSim takes as input a netlist that describes the circuit to be simulated. The initial JSim window is a very simple editor that lets you enter and modify your netlist. You may find the editor unsatisfactory for large tasks—it’s based on the JTextArea widget of the Java Swing toolkit that in some implementations has only rudimentary editing capabilities. If you use a separate editor to create your netlists, you can have JSim load your netlist files when it starts: athena% jsim filename … filename & Running standalone First, you'll need to install a Java system. The Sun Java Runtime Environment, Standard Edition (J2SE), for Linux, Solairs and Windows can be downloaded from http://java.sun.com. J2SE for Mac OS X is available from http://www.apple.com/java. On Linux, you'll want to change your PATH environment variable so that the "java" command is on your search path. On Windows and OS X, double-clicking any of the 6.004 jar files will run the program (assuming you've installed the Sun Java environment). the Sun Java environment)....
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