Logisim 2.7.0 has simulation tree, much more


Logisim, a graphical design and simulation tool for logic circuits, is now at version 2.7.0. The new version includes numerous enhancements and fixes; the most radical are a new Wiring library, a new method for drawing splitters, and enhancements to the main window's left-side explorer and attribute pane.

This version introduces the "Wiring" library, into which have been moved the circuit components previously found in "Base": splitter, pin, probe, clock, tunnel, pull resistor, and bit extender (and also constant, previously located in "Gates"). Additionally, the "Wiring" library now includes a transistor, transmission gate, power, and ground.

Another major change was in how splitters are drawn. The new technique conforms more closely to traditional circuit diagrams, and it includes labels showing the bit(s) to which each split end corresponds. The new "Appearance" attribute allows one to continue using the older technique, and projects created in older versions of Logisim will continue to load using this legacy support. However, projects can easily switch to the new appearance with labels by changing the splitters' Appearance attribute to "Centered".

The GUI has also received several updates. The explorer pane in the upper left corner has traditionally shown the current project's circuits and libraries; this is now called its "Toolbox" view. However, one can switch the explorer pane to instead show the "Simulation Tree," which includes a toolbar for controlling the simulation and the hierarchy of subcircuits in the current simulation. This provides a visualization of the full hierarchy as well as an alternative to right-clicking subcircuits (or double-clicking them using the Poke Tool) to descend into viewing their states. Another notable enhancement to the GUI is an addition of a title bar to the attribute table, which indicates whose attributes are currently being displayed.

Additional features include a Greek translation of the GUI elements, labels specific to one instance of a subcircuit, an enable input for multiplexers/demultiplexers/decoders, an Output Value attribute for gates allowing them to emit floating values (permitting wired-and and wired-or logic), and support for product-of-sums expressions in the combinational analysis module. This version also marks the removal of the Legacy library and other code meant for supporting projects built in Logisim 1.0. And the "project toolbar" - previously disabled by default - is now always enabled.

Educational institutions around the world use Logisim as an aid to teaching about digital logic and computer architecture. As a Java application, Logisim can run on most major operating systems. Read more about Logisim at http://www.cburch.com/logisim/, and download it from SourceForge.net at http://sourceforge.net/projects/circuit/.

Posted by Carl Burch 2011-03-07

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