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	<title>The Simulation tab</title>
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<h1>The Simulation tab</h1>

<p>The Simulation tab allows configuration of the algorithm used for
simulating circuits. These parameters apply to all circuits being
simulated in the same window, even for circuits that exist in other
libraries loaded within the project.</p>

<center><img src="../../../img-guide/opts-simulate.png" width="376" height="334"></center>

<ul>

<li><p>The <strong>Iterations Until Oscillation</strong> drop-down menu
specifies how long to simulate a circuit before deciding that it is
oscillating. The number represents the number of clicks of the internal
hidden clock (a simple gate takes just one click). The default of 1,000
is good enough for almost all purposes, even for large circuits. But you
may want to increase the number of iterations if you are working with a
circuit where Logisim reports false oscillations. This is unlikely to be a
problem in practice, but one such a circumstance is a circuit that incorporates
many of the below latch circuits with random noise enabled. You may want to
decrease the number of iterations if you are working with a circuit that is
prone to oscillating and you are using an unusually slow processor.</p></li>

<li><p>The <strong>Gate Output When Undefined</strong> drop-down menu configures
how the built-in logic gates behave when some inputs are unconnected or are
floating. By default, Logisim ignores such inputs, allowing a gate to work over
fewer inputs than it was designed for. However, in real life, a gate will behave
unpredictably in such a situation, and so this drop-down menu allows one to
change the gates so that they treat such disconnected inputs as errors.</p></li>

<li><p>The <strong>Add Noise To Component Delays</strong> checkbox
allows you to enable or disable the random noise that is added to the
delays of components. The internal simulation uses a hidden clock for
its simulation, and to provide a somewhat realistic simulation, each
component (excluding wires and splitters) has a delay between when it
receives an input and when it emits an output. If this option is
enabled, Logisim will occassionally (about once every 16
component reactions) make a component take one click longer than
normal.</p>

<p>I recommend keeping this option off, as this technique does introduce rare
errors with normal circuits.</p></li>

</ul>

<p><strong>Next:</strong> <a href="toolbar.html">The Toolbar tab</a>.</p>

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