vhdl-file-name-case

vhdl-file-name-case is a variable defined in `vhdl-mode.el'.
Its value is

identity

Documentation:
Specifies how to change case for obtaining file names.
When deriving a file name from a VHDL unit name, case can be changed as
follows:
As Is: case is not changed (taken as is)
Lower Case: whole name is changed to lower case
Upper Case: whole name is changed to upper case
Capitalize: first letter of each word in name is capitalized

You can customize this variable.