Hints, Tips and Solutions - December 1997


Q1: When I plot my design on a laser printer some regions are not plotted at all.

Q2. Stipple patterns on screen and on plot look differently.

A: In both cases the reason is the same. Unfortunately, color capabilities of screen and plotting devices often do not match. In particular, some non-saturated colors clearly visible on the screen are mapped into white color on drawing. We are planning to add color remapping capabilities for plot setup. At the moment, however, if you are not satisfied with colors of drawing, you may do the following.

  • Select screen colors that are mapped to plotter colors in a satisfactory way by trial printing of a set of sample color boxes
  • Prepare an alternative technology file either using a text editor or from within Expert as follows:
  • Change layer colors using Layer Setup
  • Save the technology file (using menu command Project>>Save Technology) under another name. In fact, you should have as many alternative tch files as you have different plotting devices
  • If you want to print the project only once, just change layer colors and print. If you want to print in several separate sessions, you must
  • Save your project/cell as gdsII file;
  • Read from gdsII file using an alternative technology file;
  • Plot


Q: How can I select an object if it is completely covered by other layout objects?

A: There are two ways to do this.

(1) If you know the layer of the required object, you may hide the overlaying layers.

(2) If you do not know the layer or the objects are overlapping in the same layer, or if you simply do not want to mess with layer visibility, you may use the Locate operation as follows:

  • On the Locate bar check the box “Top Level Only”. Under this option Locator will pick objects that are normally picked by Select operation, i.e., in the top level of the current cell.

Figure 1. Menu for locating
obscured objects.

  • Draw a selection box;
  • Click right mouse button (or Next button on the Locate bar) several times until you see the required object highlighted.
  • Click “Select” button on the Locate bar.

As you see from the Locate bar, there is an option to make the chosen object selected in the corresponding cell when you enter Edit-in-Place from Locate operation.


Q: I run DRC, find one or two violations, correct them, then I re-run DRC to check whether my corrections worked. However re-running on the whole design is time-consuming. How can I run DRC over the section of the layout in the vicinity of the introduced changes only?

A: Now you may do this in one of the two ways:

(1) You may select objects by box and run a script on selected objects. However this run will work only on top-level objects of the current cell. Instances will not be processed by such check. You may explode the instance several times until the selected objects are flattened and then run the check. This approach has a number of drawbacks. You must backup the original design and the DRC will not be hierarchical.

(2) You may clip out the selected region (using the Tools>>Clip Out command) and run DRC on the clipped piece. The coordinates in the clipped piece are the same as in the original design, so that you can locate errors in the original, since errors are reported as segments with coordinates of their ends. The drawbacks are spurious error reports along the clip boundary and “semiautomatic” error location. However you will get hierarchical DRC.