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6: Exports |
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All nodes in Electric have connection sites, called ports, which indicate where wires may be attached. The primitive nodes have predefined ports, but ports on facet instances must be defined by the user. To do this, simply select a port on a node inside the facet, and turn it into an export, which makes it available on all instances of the current facet. Although most ports are on nodes along the edge of the facet, Electric makes no port location restrictions, so they may appear anywhere.
To create an export, select a port on a node and use the Create Export... command of the Export menu. The resulting dialog requests an export name and some characteristics. All export names on a facet must be unique; if a nonunique name is given, it is modified (by adding "_1", "_2", and so on) to be unique. Like facet names, export names may not contain spaces, tabs, or unprintable characters, and no case distinction is made between uppercase and lowercase characters. | ![]() |
Behavioral characteristics can be associated with an export by selecting the appropriate field in the export creation dialog. These behavior characteristics are stored with the export and used primarily by simulators.
The "Always drawn" check box requests that the export label should always appear, regardless of the connection or expansion of its facet. Typically, an export label on an instance of a facet is not displayed when that port is connected to an arc or when the instance is expanded. This check box overrides the suppression.
Another special check box, "Body only," requests that this export not appear when an icon is generated for the facet. This is useful for power and ground exports or duplicate connection sites on a single network.
There are two special exporting commands that are primarily used in array-based layout. If a facet instance is replicated many times and the instances are wired together, then ports on the edge of the array are the only ones that are not wired. These ports define the connections for the next level of hierarchy. What you want to do is to create exports for all unwired ports on all facet instances. To do this, use the Re-Export Everything command of the Export menu, which generates unique names as it exports all unwired ports on facet instances. To do this same function, but only in the currently highlighted area, use Re-Export Highlighted. Note that ports on primitive nodes are not exported with these commands. See Section 6-4 for more about arrays, and see Section 9-5 for more on automatic wiring.
Another special case in export creation is the Add Export from Library... command, which copies exports from another library to the current one. The other library is examined for facets whose names match ones in the current library. When a facet is found in the other library, all of its exports are copied to the facet in the current library (if they don't already exist). This command is useful in managing standard cell libraries that are imported from other file formats (see Section 3-9 on Standard Cell Libraries). Because some formats contain geometry and others contain connectivity, this command is needed to put them together.
Exports are selected by clicking on their text, or by clicking on the node from which they are exported. If a very dense design makes mouse selection hard, you can select exports from a list by using the Select Export... subcommand of the Selection command of the Edit menu.
Once a port has been exported, its characteristics can be modified by selecting the export name and using the Get Info command of the Info menu. In addition to allowing the export name and characteristics to be changed, the dialog allows the size and placement of the export text to be modified. See Section 6-8 for more about export size and placement. | ![]() |
Exports can be displayed on the screen in many different ways. The Export Display Options... command of the Export menu provides four options: "Full Export Names" shows full text names, "Short Export Names" shows export names only up to the first nonalphabetic character, "Exports as Crosses" shows crosses at the export locations, and "No Exports Shown" indicates that no exports are to be displayed. With short export names, the exports "Power-left" and "Power-1" are both written as "Power," which allows multiple exports with the same functionality but different names to be displayed as if they have the same name. | ![]() |
You can delete an export simply by selecting its name and typing the delete key. You can also use the Delete Export command of the Export menu.
To remove many exports at once, the Delete All Export on Highlighted command removes all exports on all highlighted nodes. Also, the Delete All Export in Area command removes only those exports that are in the selected area (use the rectangle select button to define a precise area). When an export is deleted, all arcs connected to that port on instances of the current facet (higher up the hierarchy) are also deleted.
It is sometimes desirable to keep an export but to transfer it to another node. If a facet is in use higher in the hierarchy, unexporting and then reexporting deletes all existing connections. Instead, the Move Export command of the Export menu can be used. Before using this command, two nodes and their ports must be highlighted with selection button and toggle select button. The export is moved from the first node to the second node.
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