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Node Mapping

It is often desirable to use textual node names instead of the integers assigned by Xic as node references in SPICE output. This at times produces more readable SPICE output, and may be essential if the output is processed by other applications. A problem is that Xic generates the default node numbering internally, thus it may vary unpredictably if the circuit is modified. By using node names supplied by the user or based on the strings of attached vcc devices and terminal names, the node names become predictable and repeatable after circuit modification.

Node mapping is enabled by activating the nodmp button in the electrical mode side menu. When the nodmp button is on, node mapping will be performed when SPICE output is created. A property is added to the current cell, so the initial state of the nodmp button represents the state under which the cell was saved.

Pressing the nodmp button, when inactive, brings up the Node Mapping panel. If the button is active, one should turn the button off, then on again to bring up the panel. The panel has four buttons: Dismiss, Rename, Remove, and Point. The Dismiss button retires the panel, without changing the state of the nodmp button. The Rename button allows a name to be given to a selected node. The Remove button will delete the name assignment of the selected node, if one was given previously with the Rename button. The Point button, when active, allows nodes to be selected in the panel display by clicking on nodes in the drawing window.

The panel contains two text areas, with the left area listing the nodes, and the right area listing the device and subcircuit terminals connected to the selected node. Nodes can be selected by clicking on the text in the left text window, or by clicking in the circuit if the Point button is active.

The left column in the node listing contains the internal node numbers, which can change arbitrarily if the circuit is modified. Entries in the second column are the mapped names, i.e., the names used in SPICE and netlist files when node mapping is active. If the second column entry is blank, the internal node number will be used.

The entry in the second column will be blank unless:

  1. The node has been assigned a name with the Rename button.
  2. The node is connected to a vcc type of device.
  3. The node is connected to one of the cell terminals.
The precedence is in the order listed. If an entry exists in the second column, that token will indicate the node. This will not change if the circuit changes.

Node mapping is performed only when the nodmp button is active. When the button is inactive, the internal number will be used for all nodes.

The node referencing works by association with a device terminal. This association persists if the object is moved, and is transferred to another device or wire if the object is deleted, if possible. In some cases it may get lost, however, so an assigned name may have to be reentered.

The names used for device terminals are the terminal names as supplied in the node properties in the device library file. However, only ``physical'' terminals will have an assigned name. Device contacts such as the phase node of a Josephson junction, branch nodes, and nodes of current and voltage sources have no implementation in a physical layout and have no names. In the listing in the right-hand panel, the terminal name for these ``unnamed'' terminals is constructed as devicename_contactnum. That is, the device name, followed by an underscore, followed by an internal index number for contacts of that device or subcircuit (subcircuits may have non-implemented contacts as well).

When a node is selected, a small box is shown over all associated connections in the electrical view.


next up previous contents index
Next: The plot Button: Generate Up: The nodmp Button: Enable Previous: The nodmp Button: Enable   Contents   Index
Stephen R. Whiteley 2006-10-23