Liberty interface_timing attribute

[k31th1408]

Someone suggested to use interface_timing=true for latches in .lib file. I cannot find info on what this attribute really does. In the Liberty reference manual, it says

Indicates that the timing arcs are interpreted according to interface timing specifications
semantics. If this attribute is missing or its value is set to false, the timing relationships
are interpreted as those of a regular cell rather than according to interface timing
specification semantics.

The problem is that this definition does not describe what "interface timing specifications
semantics" are and how it affects timing reports. Anyone have more info on this? Thanks!

 

[dmedlock]

Someone suggested to use interface_timing=true for latches in .lib file. I cannot find info on what this attribute really does. In the Liberty reference manual, it says

Indicates that the timing arcs are interpreted according to interface timing specifications
semantics. If this attribute is missing or its value is set to false, the timing relationships
are interpreted as those of a regular cell rather than according to interface timing
specification semantics.

The problem is that this definition does not describe what "interface timing specifications
semantics" are and how it affects timing reports. Anyone have more info on this? Thanks!

interface_timing=true is used for arbitrary cells that don't have a function or state table description. The timing arcs are used as-is with no attempt to validate them against a function. As such, this is not the best way to model a latch. If it's simple just use a "latch" group. If you need something more complex you can model it with a state table.