56 Chapter
6
Design unit package
A package declaration may contain the declarations of types,
subprograms, files and so on. In this way, the reuse of description parts is
supported. The declared elements can be made visible to other design units.
The package STANDARD with declarations of standard types (for example
BIT, BOOLEAN, REAL, ...) is part of the predefined language
environment.
Design unit package body
A package body contains hidden parts of a package. For instance, the
interface declaration of a subprogram is described in the package
declaration. The package body contains the full program code. Its details are
hidden outside the package.
6.2.2
Logical libraries and compilation of design units
Administration of analyzed design units
The design units are compiled into design libraries. The compilation
consists of
Analysis of the source code description
Generation of an intermediary code which is saved in a design library
A design library must be created and managed using commands that
depend on the specific simulation engine used. A physically existing design
library is connected with a specific logical name. In VHDL-AMS
descriptions, only the logical names are important and used. There are
several kinds of design libraries. Compilation is usually done in the WORK
library. Predefined libraries are available in the simulation environment and
can be used as resource libraries. Examples are the STD library and the
IEEE library.
WORK library
Compiled design units are by default placed into the working design
library named WORK.
STD library
The STD library contains the standard packages STANDARD and
TEXTIO. The packages predefine basic language types, subtypes, and