ModelSim SE User's Manual - Electrical and Computer Engineering

Compiling VHDL files
Creating a design library
Compiling VHDL files UM-73
Before you can compile your source files, you must create a library in which to store the
compilation results. Use vlib (CR-356) to create a new library. For example:
vlib work
Invoking the VHDL compiler
Dependency checking
This creates a library named work. By default, compilation results are stored in the work
library.
The work library is actually a subdirectory named work. This subdirectory contains a
special file named _info. Do not create libraries using UNIX, MS Windows, or DOS
commands – always use the vlib command (CR-356).
See "Design libraries" (UM-57) for additional information on working with libraries.
ModelSim compiles one or more VHDL design units with a single invocation of vcom (CR-
311), the VHDL compiler. The design units are compiled in the order that they appear on
the command line. For VHDL, the order of compilation is important – you must compile
any entities or configurations before an architecture that references them.
You can simulate a design containing units written with 1076 -1987, 1076 -1993, and
1076-2002 versions of VHDL. To do so you will need to compile units from each VHDL
version separately. The vcom (CR-311) command compiles using 1076 -2002 rules by
default; use the -87 or -93 argument to vcom (CR-311) to compile units written with version
1076-1987 or 1076 -1993, respectively. You can also change the default by modifying the
VHDL93 variable in the modelsim.ini file (see "Preference variables located in INI files"
(UM-524) for more information).
Dependent design units must be reanalyzed when the design units they depend on are
changed in the library. vcom (CR-311) determines whether or not the compilation results
have changed. For example, if you keep an entity and its architectures in the same source
file and you modify only an architecture and recompile the source file, the entity
compilation results will remain unchanged and you will not have to recompile design units
that depend on the entity.
ModelSim SE User’s Manual