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- <title>Editing the truth table</title>
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- <h1>Editing the truth table</h1>
- <p>On opening the Combinational Analysis window, you will see that
- it consists of five tabs.
- <center><img src="../../../../en/img-guide/analyze-var.png" width="466" height="321"></center>
- This page describes the first three tabs, Inputs, Outputs, and Table.
- The next page of the guide describes the last two tabs,
- Expression and Minimized.</p>
- <h2>The Inputs and Outputs tabs</h2>
- <p>The Inputs tab allows you to view and edit the list of inputs.
- To add new inputs, type it in the field at the pane's bottom,
- and click Add. If you want to rename an existing input, select it
- in the list in the pane's upper left region; then type the name
- and click Rename.</p>
- <p>To remove an input, select it from the list and click Remove.
- You can also reorder the inputs (which affects the order of
- columns in the truth table and in the generated circuit) using
- the Move Up or Move Down buttons on an input.</p>
- <p>All actions affect the truth table immediately.</p>
- <p>The Outputs tab works in exactly the same way as the Inputs tab,
- except of course it works with the list of outputs instead.</p>
- <h2>The Table tab</h2>
- <p>The only item under the Table tab is the current truth table,
- diagrammed in the conventional order, with inputs constituting the
- columns on the left and outputs constituting the columns on the
- right.</p>
- <p>You can edit the current values appearing in the output columns by
- clicking on the value of interest. The values will cycle through 0,
- 1, and <em>x</em> (representing a "don't care"). As we'll see on the
- next page, any don't-care values allow the computation of
- minimized expressions some flexibility.</p>
- <p>You can also navigate and edit the truth table using the keyboard.
- And you can copy and paste values using the clipboard. The clipboard
- can be transferred to any application supporting tab-delimited text
- (such as a spreadsheet).</p>
- <p>If the truth table is based on an existing circuit,
- you may see some pink squares in the output columns with "!!" in them.
- These correspond to errors that occurred while calculating the value
- for that row - either the circuit seemed to be oscillating, or the
- output value was an error value (which would be pictured as a red wire
- in the Logisim circuit). Hovering your mouse over the entry should
- bring up a tool tip describing which type of error it was. Once you
- click on the error entry, you will be in the 0-1-<em>x</em> cycle;
- there is no way to go back.</p>
- <p><strong>Next:</strong> <a href="expr.html">Creating expressions</a>.</p>
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