Chapter VII: DESIGN ENVIRONMENTS

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2: Units

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Electric stores all geometry in terms of an internal unit of distance, but displays all distances in terms of a display unit. Users need not be aware of the internal unit value, because Electric always uses the display unit in all interaction.

To allow scalable designs, the display unit can be the scalable distance lambda. The use of lambda-based design allows design rules to be specified in a general way and scaled with the process. Designers need only know that their transistors must be 2x2 lambda units, and do not need to concern themselves with the value of lambda (which is shown in the status area).

Figure 7.1
To change the value of the internal unit, the display unit, or the value of lambda, use the Change Units... command of the Technology menu. Be careful if you change the internal database unit, because this may result in all data being scaled, which may not be desirable.

When you change the display units, it only affects how numbers are presented, not their internal storage. For example, selecting the "Microns" display unit causes Electric to describe distances in microns, rather than lambda units. When a real display unit is used, appropriate notation is used to express distances (i.e. a 3 micron wire is "3u" wide).

By default, when you type a distance value in Electric, that value is presumed to be in lambda units. However, if you add a specific unit symbol to the end of the value, those units are used. These unit symbols are recognized:

Unit
Unit Symbol
Example
Inches
"
3"
Centimeters
cm
7cm
Millimeters
mm
12mm
Mils
mil
4.5mil
Microns
u
-90u
Centimicrons
cu
100cu
Millimicrons
mu
1mu


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