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<doc>

  <title>Connectivity</title>

  <p>
  Use the connectivity page to specify the conductor layers and their connections.
  On a conductor layer, all touching or overlapping shapes are connected.
  A connection is made between conductor layer when the shapes of the two conductor layers overlap. 
  Optionally a via layer can be specified which must be present to make a connection between the two conductor layer.
  </p>

  <p>
  To specify a conductor layer
  </p>

  <ul>
    <li>
      Use "layer/datatype" notation to specify explicit GDS layers and datatypes.
    </li>
    <li>
      Enter the layer name to specify either a named layer or a symbolic layer.
      Symbolic layers must be defined in the symbol table (see <link href="/about/symbolic_layers.xml"/>) 
      and can be computed from boolean expressions.
    </li>
    <li>
      Instead of using a symbolic layer, 
      enter a expression directly without defining a symbol (see <link href="/about/symbolic_layers.xml"/>).
      Inside the expressions
      <ul>
      <li>
        Use "layer/datatype" notation to specify an original layer with explicit GDS layers and datatypes.
      </li>
      <li>
        Use the name to specify a named original layer or to refer to a different symbolic layer defined in a symbol entry.
      </li>
      <li>
        Use the operators '+', '*', '-' and '^' to specify logical OR, AND, NOT and XOR respectively. 
        The precedence of evaluation is '^' and '*' before '+' and '-'.
      </li>
      <li>
        Use round brackets to group expressions.
      </li>
      </ul>
    </li>
  </ul>

  <p>
  By creating conductor layers with boolean expressions, it is possible for example to separate an active area
  layer of a CMOS transistor into source and drain regions by subtracting the gate poly. Symbolic layers are useful
  to use "speaking" names for layers instead of the numeric layer/datatype specificiation.
  Please note, that the net tracer is considerably slower when using boolean expressions.
  </p>

</doc>


