Compiling and Simulating - 2025.2 English - UG900

The Vivado simulator executable xvhdl converts a VHDL design unit into parser dump (.vdb). By default, Vivado simulator uses mixed 93 and 2008 standard (STD) and IEEE packages to freely allow mixing of 93 and 2008 features. If you want to force only the VHDL-93 standard (STD) and IEEE package, use only xvhdl. To compile a file only with VHDL 2008 mode, you need to pass -2008 switch to xvhdl.

For example, to compile a design called top.vhdl in VHDL-2008, the following command line can be used:

xvhdl -2008 -work mywork top.vhdl

The Vivado simulator executable xelab elaborates a design and produce an executable image for simulation.

xelab can do either of the following:

• Elaborate on parser dumps produced by xvhdl
• Directly use vhdl source files.

No switch is needed to elaborate on parser dumps produced by xvhdl. You can pass -vhdl2008 to xelab to directly use vhdl source files.

Example 1:

xelab top -s mysim; xsim mysim -R

Example 2:

xelab -vhdl2008 top.vhdl top -s mysim; xsim mysim -R

Instead of specifying VHDL files in the command line for xvhdl and xelab, a .prj file can be used. If you have two files for a design called top.vhdl (2008 mode) and bot.vhdl (93 mode), create a project file named example.prj as follows:

In the project file, each line begins with the file's language type such as vhdl, followed by the library name such as xil_defaultlib. One or more file names follow with a space separator. For VHDL 93, use vhdl as the language type. For VHDL 2008, use vhdl2008 instead.

A .prj file can be used as shown in the example below:

xelab -prj example.prj xil_defaultlib.top -s mysim; xsim mysim -R

Alternatively, to mix VHDL 93 and VHDL 2008 design units, compile the files separately with a proper language mode specified to xvhdl. Then, elaborate on top(s) of the design. If you have a VHDL 93 module called bot in file bot.vhdl, and a VHDL-2008 module called top in file top.vhdl, compile them as follows:

xvhdl bot.vhdl
xvhdl -2008 top.vhdl
xelab -debug typical top -s mysim

Once the executable is produced by xelab, you can run the simulation as usual.

Example 1:

xsim mysim -gui

Example 2:

xsim mysim -R