The syntax of the set_bus_skew command with the basic options
is:
set_bus_skew [-from <args>] [-to <args>] [-through <args>] <value>The list of objects for the -from option must be a collection of
valid startpoints. A valid startpoint for set_bus_skew is the clock
pin of a sequential element, such as a register or RAM, or the sequential cell
itself. Input and inout ports are not supported as startpoints.
The list of nodes for the -to option must be a collection of valid
endpoints. A valid endpoint for set_bus_skew is the data pin of a
sequential cell or the cell itself. Output and inout ports are not supported as
endpoints.
The list of nodes for the -through options
must be a list of valid pins or nets.
-from and -to options are required
when specifying a bus skew constraint.The bus skew value must be both realistic and reasonable. AMD recommends using a value that is larger than half the minimum period of the source and destination clocks. The appropriate value for bus skew also depends on the clock domain crossing (CDC) topology, as demonstrated by the following examples.