| 12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970717273747576777879808182838485 |
- <html>
- <head>
- <title>Adder</title>
- </head>
- <body bgcolor="FFFFFF">
- <h1><img align="center" src="../../../icons/adder.gif" width="32" height="32">
- <em>Adder</em></h1>
- <p><table>
- <tr><td><strong>Library:</strong></td>
- <td><a href="index.html">Arithmetic</a></td></tr>
- <tr><td><strong>Introduced:</strong></td>
- <td>2.0 Beta 11</td></tr>
- <tr><td valign="top"><strong>Appearance:</strong></td>
- <td valign="top"><img src="../../../img-libs/adder.png" width="44" height="45"></td></tr>
- </table></p>
- <h2>Behavior</h2>
- <p>This component adds two values coming in via the west inputs and
- outputs the sum on the east output. The component is designed so that it
- can be cascaded with other adders to provide add more bits than is
- possible with a single adder: The carry-in input provides a
- one-bit value to be added into the sum also (if it is specified), and a
- carry-out output provides a one-bit overflow value that can be fed to
- another adder.</p>
- <p>If either of the addends contains some floating bits or some error
- bits, then the component will perform a partial addition. That is, it
- will compute as many low-order bits as possible. But above the floating
- or error bit, the result will have floating or error bits.</p>
- <h2>Pins</h2>
- <dl>
- <dt>West edge, north end (input, bit width matches Data Bits attribute)
- <dd>One of the two values to add.
- <dt>West edge, south end (input, bit width matches Data Bits attribute)
- <dd>The other of the two values to add.
- <dt>North edge, labeled <var>c in</var> (input, bit width 1)
- <dd>A carry value to add into the sum. If the value is unknown (i.e.,
- floating), then it is assumed to be 0.
- <dt>East edge (output, bit width matches Data Bits attribute)
- <dd>The lower <var>dataBits</var> bits of the sum of the two values
- coming in the west edge, plus the <var>c</var><sub><var>in</var></sub>
- bit.
- <dt>South edge, labeled <var>c out</var> (output, bit width 1)
- <dd>The carry bit computed for the sum. If the values added together as
- unsigned values yield a result that fits into <var>dataBits</var>
- bits, then this bit will be 0; otherwise, it will be 1.
- </dl>
- <h2>Attributes</h2>
- <p>When the component is selected or being added,
- Alt-0 through Alt-9 alter its <q>Data Bits</q> attribute.</p>
- <dl>
- <dt>Data Bits</dt>
- <dd>The bit width of the values to be added and of the result.</dd>
- </dl>
- <h2>Poke Tool Behavior</h2>
- <p>None.</p>
- <h2>Text Tool Behavior</h2>
- <p>None.</p>
- <p><a href="../index.html">Back to <em>Library Reference</em></a></p>
- </body>
- </html>
|
