tom logic chips.  (located under "Digital Chips")
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Every custom logic device has a model name, which points to a model that describes how it works.  You can have any number of
devices with the same model.  Editing the model changes the behavior of all devices that use that model.
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When editing the model, you specify the inputs, the outputs, some info text (which is shown in the lower right
corner when hovering the mouse over a device), and the definition.
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The inputs (and outputs) is a comm