Pins Selection for Optimization

You can choose to optimize all pins or only a few selected pins in the design. To select the required pins, either select the individual pins or select the nets, instances, or PR boundary that contain the required pins. In addition, you can use the VFP_EXT_MULTIFIG_THRESHOLD SHELL environment variable to filter out the required pins from the selected pins. Use this environment variable to choose the nets that contain the required number of pins. For example, if the VFP_EXT_MULTIFIG_THRESHOLD SHELL environment variable is set to 2, then the pins of only those nets that connect two pins or less are selected for optimization. Pins connected to the remaining nets are treated as fixed pins, and are therefore not optimized. Therefore, this environment variable serves as an additional check on the number of pins selected for optimization.

The default value of the VFP_EXT_MULTIFIG_THRESHOLD SHELL environment variable is 50, which is used by Pin Optimizer in the default mode. To optimize the pins of nets that have not been selected as a result of the default value 50, increase the threshold value.

For example, to increase the threshold to value 100:

setShellEnvVar(“VFP_EXT_MULTIFIG_THRESHOLD” “100”)

For example, to decrease the threshold to value 2:

setShellEnvVar(“VFP_EXT_MULTIFIG_THRESHOLD” “2”)

Related Topics

Planning Placement of Top-Level and Level-1 Pins

Support for Net PRO Definitions