Libraries and Packages

Design libraries are used to collect design units into uniquely-named areas that can be referenced from multiple source files in your design. Design units are the main components of a VHDL description. The primary design units are entities, packages and configurations. The secondary design units are architectures and package bodies. The secondary design units depend on the specification of their interface in a corresponding primary design unit.

A package is a collection of commonly-used declarations such as types, constants, subprograms, etc. The contents of a package can be used throughout the design, or in multiple projects.

The library and use clauses have to be used to make the contents of a library and package visible in a design unit.