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The wire Button: Create/Edit Wires

\epsfbox{wire.eps}

The wire button is used to create or modify wires. A wire is created by clicking the left mouse button on each vertex location in sequence, and is terminated by clicking on the final vertex twice. In electrical mode, wires are used to connect devices into circuits. Vertices are recognized as connecting points, and are created where the wire crosses a device or subcircuit terminal or a vertex of another wire. The Connection Dots button in the Attributes Menu can be used to display connections. The vertices can be edited to remove or reestablish connections.

In electrical mode, entering the wire command will switch the current layer to the SCED (active) layer. The current layer can be changed if necessary, but without the reverting it was too easy to create wires on another layer, sometimes difficult to visually differentiate, that will not be electrically active in the schematic causing the circuit to not work.

While the command is active in physical mode, the cursor will snap to horizontal or vertical edges of existing objects in the layout if the edge is on-grid, when within two pixels. When snapped, a small dotted highlight box is displayed. This makes it much easier to create abutting objects when the grid snap spacing is very fine compared with the display scaling. This is also applied to the last vertex of wires being created, facilitating point list termination. This feature can be controlled from the Edge Snapping group in the Snapping page of the Grid Setup panel.

When adding vertices during wire creation, the angle of each segment can be constrained to a multiple of 45 degrees with the Constrain angles to 45 degree multiples check box in the Editing Setup panel from the Edit Menu, in conjunction with the Shift and Ctrl keys. There are three modes: call them ``no45'' for no constraint, ``reg45'' for constraint to multiples of 45 degrees with automatic generation of the segment from the end of the 45 section to the actual point, and ``simp45'' that does no automatic segment generation. The ``reg45'' algorithm adds a 45 degree segment plus possibly an additional Manhattan segment to connect the given point. The ``simp45'' adds only the 45 degree segment. The mode employed at a given time is given by the table below. The Constrain45 variable tracks the state (set or not set) of the check box.

Constrain45 not set
  Shift up Shift pressed
Ctrl up no45 reg45
Ctrl pressed simp45 simp45
Constrain45 set
  Shift up Shift pressed
Ctrl up reg45 no45
Ctrl pressed simp45 no45

In physical mode, three end styles are available for nonzero width wires: Flush, Rounded, and Extended. The end style and the default width are set from the menu provided by the style button. The end style of selected wires can be changed from this menu, from within the wire command or without.

The width of wires on a particular layer, or the widths of existing wires, can be set of changed with the Wire Width button in the menu brought up with the style button. Zero-width wires are accepted into the database if they contain more than one point. In physical mode, they probably should not be used, and they will, of course, fail DRC tests. They are allowed in the off chance that the user uses them for annotation purposes. Such lines will be invisible, however, unless the layer pattern is outlined or solid. In electrical cells, zero-width wires are commonly used for the connecting lines, and there is no question of their legality in electrical cells. The width of selected wires can be changed with this menu command, from within the wire command or without.

If the first vertex of a wire being created falls on an end vertex of an existing wire on the same layer, the new wire will use the same width and end style as the existing wire, overriding the defaults. The completed new wire will be merged with the existing wire, unless merging is disabled. Merging can be controlled from the Editing Setup panel from the Edit Menu, and note also that the NoMerge layer attribute will prevent merging.

Wires with a single vertex are acceptable if the width is nonzero and the end style is rounded or extended. These are rendered as an octagon or box, respectively, centered on the vertex.

Existing wires can be converted to polygons through selection and execution of the polyg command.



Subsections
next up previous contents index
Next: Wire Vertex Editor Up: The Side Menu: Geometry Previous: The terms Button: Show   Contents   Index
Stephen R. Whiteley 2017-04-09