Constants - 2023.1 English - UG901

SystemVerilog gives three types of elaboration-time constants:

• parameter: Is the same as the original Verilog standard and can be used in the same way.
• localparameter: Is similar to parameter but cannot be overridden by upper-level modules.
• specparam: Is used for specifying delay and timing values; consequently, this value is not supported in Vivado synthesis.

There is also a runtime constant declaration called const.