next up previous contents index
Next: Xic Configuration and Startup Up: Database Overview Previous: Cell Hierarchy Digest   Contents   Index

Database Resolution

By default, Xic uses an internal resolution of 1000 units per micron. In releases prior to 3.0.12, this was internally hard-coded. As the dimensions used in integrated circuits continue to shrink, an option for higher resolution has been added.

The resolution can be set with the DatabaseResolution variable, which can be set to ``1000'', ``2000'', ``5000'', or ``10000''. If unset, 1000 units is used. This resolution applies only to physical data, electrical resolution is fixed at 1000.

This variable can be set only from the .xicinit file, which is read before the technology file, or the technology file. It can not be set or unset in a .xicstart file (read after the technology file) unless no technology file is read, or by any other means. It is important that the resolution be set before reading such things as DRC rules, since the rules contain resolution-dependent numbers which would be incorrect after a resolution change.

Superficially, changing the internal resolution has only subtle effects from the user's vantage point. Some of these are:

  1. If not 1000, four digits following the decimal point are used when printing coordinates in microns, in many places in Xic. Otherwise, only three digits are used.

  2. The ultimate zoom-in and grid spacing sizes are smaller for higher resolutions.

  3. The size of ``infinity'', the maximum accessible size for the design, becomes smaller as resolution is increased, since coordinates are stored internally as 32-bit integers. For 1000 units, the field width is approximately 2 meters, which decreases to 20 centimeters at 10000 units. This should still be plenty for most purposes.

  4. Layout files produced by Xic will use the internal resolution, so that no accuracy is lost.

Unless there is a specific need, it is recommended that users employ the default resolution.


next up previous contents index
Next: Xic Configuration and Startup Up: Database Overview Previous: Cell Hierarchy Digest   Contents   Index
Stephen R. Whiteley 2017-03-22