LEF API Reference

The LEF API reference is copyrighted by Cadence (http://www.cadence.com) under the Apache License, Version 2.0 and is available here: LEF API

Implementation Notes

Understanding Units

In the UNITS section, the statement:

DATABASE MICRONS LEFconvertFactor

Means that:

  1. The distances in the lef file are expresseds (always, it seems) in micrometers.

  2. The distances are multiples of \frac{1}{LEFconvertFactor} which is the smallest amount of distance we can represent. By default LEFconvertFactor is set to 100, which means steps of 0.01µm.

    This is the equivalent of the precision factor in the Hurricane database.

Callback Calling Order

The callback for the PIN section is called before the callback of the whole MACRO it belongs to.

As a consequence, we have to create Net before the Cell can be known. To avoid transient storage of lots of informations while we are reading the PIN, when we encounter one and no temporary Cell exists, we create one named "LEFImportTmpCell". This temporary Cell will be renamed and configured when the subsequent MACRO callback is called.