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发表于 2012-11-20 22:47:22
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DESCRIPTION |
Sets the min_capacitance attribute to capacitance_value on the specified input ports. compile attempts to ensure that the load driven by the input port is not reduced below capacitance_value. The minimum capacitance value for a net is defined as the greatest of the minimum capacitance values of the driving cell pins and ports on a net.
If min_capacitance attributes are already specified in a technology library (implicit constraints), compile automatically tries to meet them.
By default, a port has no min_capacitance constraint.
min_capacitance, along with max_fanout and max_transition, is a design rule constraint; max_delay and max_area are optimization constraints. Design rule constraints reflect those technology-specific restrictions that must be met for a design to function correctly, while optimization constraints reflect goals and restrictions that are desirable, but not crucial for the operation of a design. Design Compiler attempts to meet all constraints placed on a design, but gives priority to design rule constraints in the optimization process. Therefore, compile gives preference to min_capacitance and other design rule constraints, even if they adversely affect optimization constraints on a design.
To get information about optimization and design rule constraints, use report_constraint; to get information on the current port settings, use report_port. To remove the min_capacitance attribute from a port, use remove_attribute. |
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发表于 2012-11-20 22:17:12
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