Version Incompatibility List

One of the primary design goals of the incremental development plan for LC is to have upward compatibility for model files. This means that a model created and run under an older version of LC should run the same and produce the same results if run using a newer version.

As a secondary goals is downward compatibility. This means that a model created using a newer version of LC will usually run the same under an older version. Of course, any new features used by the model that did not exist in the older version will be ignored.

From time to time, the decision is made to forgo strict upward or downward compatibility. Sometimes the implementation would be too difficult, or the change is seen as a fix for an undesireable behavior.

Known Compatibility Violations

LC 2.3f Power density returns watts/meter2
Some previous versions returned power density as watts/cell, even though it was labelled as watts/meter2. This calculation varied with the cell size. The difference between the old and new calculations is a constant scale factor.
 
LC 2.1c Current source and probe directions
Previously, X- and Y-directed current sources and probes followed a right-hand rule convention, but Z-directed sources and probes used a left-handed convention. Now all current sources and probes use the convention that a current that flows along an axis with increasing coordinate values is positive (right-hand convention). This inconsistency caused Z-directed SPICE circuits to work properly, while X- and Y-directed SPICE circuits caused numeric instability.
 
LC 2.1c Voltage source and probe inverted
This change was precipitated by the current fix. All voltage sources and probes are now inverted from their previous definition. This makes the voltages agree with the standard definition that voltage is the negative of the line integral of the electric field.


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Last modified Thu Feb 26 09:09:02 CST 1998