Transition violations can be fixed by different methods based on the
design situations.
They include:
* Up sizing the driver cell
* Decreasing the net length by moving cells nearer or reducing
long routed net
* By adding buffers
* By using existing spare cells as buffers
* By splitting loads through buffers to reduce the fan out number
(number of driven cells)
First we need to analyze the root causes of violations. Obstructions
such as macros, routing blockages, or fixed status of cells might have
caused long routed net lengths or detours causing increased load on
the connected driver.
Recently I had a chance to work on metal only change ECO wherein no
base layer change is carried out. The new ECO cells added are having
the same base layers. Special ECO cell library has been used for this
purpose. Here new cells have to be added wherever space available by
not moving any of the existing placed cells. Naturally placement of
the new cells were not based on connectivity of the cells rather it
was availability of the placement locations. This caused long routed
nets causing huge transition violation.
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