Dummy Instances Backannotation

Dummy instances are backannotated to the schematic to keep the two views synchronized. The criteria for backannotation are that the layout dummy instance does not have a corresponding schematic instance and the layout instance has the lxDummy property set to TRUE. Once backannotated, the ignore property on the layout dummy is removed. If there are multiple layout dummies and they have the same master, parameters, and connectivity, they can optionally be backannotated as single devices or as m-factored or iterated instances. To do this, you can set the backAnnotateInstances environment variable to "mfactored" or "iterated", which applies to the interactive backannotation command, and set the lxDummyBackAnnotateMFactor environment variable to t, which applies to the BackAnnotate All Dummies command.

For each dummy instance that is backannotated, a corresponding symbol is created in the schematic view. However, if the backannotated instances have the same master or connectivity, you can choose to backannotate them as mfactored dummy symbols. To do this, you must set the lxDummyBackAnnotateMFactor environment variable to t.

Backannotating and Customizing All Dummy Instances

To backannotate and customize all dummy instances:

1. Choose Connectivity – Back Annotate – Dummy Instance.
   Alternatively, click the toolbar button and select Back Annotate Dummy Instances.
   1. Press F3 to display the Back Annotate Dummies form.

Backannotating All Active and Inactive Dummy Instances

To backannotate all the active and inactive dummy instances:

• Choose Connectivity – Back Annotate – All Dummy Instances.
  Alternatively, click the toolbar button and select Back Annotate All Dummy Instances.
  This calls the lxHiBackAnnotateAllActiveDummies SKILL function.

To backannotate selected active and inactive dummy instances:

• Choose Back Annotate – Selected Dummy Instances.
  This calls the lxHiBackAnnotateSelectedDummies SKILL function.

To delete all schematic dummy instances:

• Choose Back Annotate – Delete All Schematic Dummy Instances.
  This calls the lxDeleteSchematicDummies SKILL function.

Although it is not recommended to edit your layout after you have backannotated the dummies, if you do make edits, it is advisable to run Check Against Source to check if any instance mismatches exist. If any discrepancies are reported, you must make the appropriate updates manually.

Let us consider that a symbol that has been backannotated from the layout is represented as a three-terminal device. After backannotation, you add a fourth terminal to the layout representation of the device.

Now, if you were to run Check Against Source to check for any instance mismatches, you will observe that a missing instance is reported in the schematic. To fix this issue, in the schematic view, you need to manually add an ignore property to the symbol that ignores the fourth or the bulk terminal of the layout device. The same property must also be added to the ignore property list in the layout.

After the ignore property is set, running Check Against Source reports no mismatches.

Related Topics

Back Annotate Dummies Form

lxDummyBackAnnotateMFactor

backAnnotateInstances

ignore Property

lxHiBackAnnotateAllActiveDummies

lxHiBackAnnotateSelectedDummies

lxDeleteSchematicDummies

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