Each ProASIC and ProASICPLUS device includes four global networks that have access to every tile. These four global networks provide high speed, low skew routing resources to signals such as clocks and global resets.
Once the netlist is imported, Designer sets global resource parameters and promotes the highest fanout nets to the remaining global resources unless the dont_fix_globals statement has been specified in a constraint file.
Note: When using the dont_fix_globals statement, global assignments made in the constraint files and design netlist will be honored (the constraint file entries will take precedence).
These global resource parameters can be supplemented by including global resource constraints in a constraint file. Global resource constraints can define which signals are assigned to global resources and which signals cannot be promoted to global resources. Global resource constraints can also override the default action that selects high fanout nets for use by the global resources.