2-3: Circuit Deletion


To remove circuitry, select nodes and/or arcs and use the Erase command from the Edit menu. A keyboard shortcut for this is the Delete key. If there is a highlighted area rather than a highlighted object, everything in the area is erased.

Note that an arc always connects two nodes, and therefore it cannot remain if one of the nodes is gone. This means that certain rules apply to circuit deletion:

(1) When a node is erased, all connecting arcs are also deleted. However, if a node is deleted that has exactly two arcs, connected as though the node were in the middle of a single arc, then the node and two arcs are replaced with a single arc.

(2) In the interest of cleanliness, if an arc is erased, any isolated pins are also erased.

(3) If an erased node has an export on it (as in the example below), then the export disappears and so do all arcs connected to the port on instances of the current cell (for more information on hierarchy, see Chapter 3).
Figure 2.6

Figure 3.14
The Erase Geometry command erases all geometry in the highlighted area. All arcs that cross into that area will be truncated. Thus, this command truly erases geometry, independent of the structure of nodes and arcs. Note that the area to be erased is adjusted by the current alignment values (see Section 4-7).

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