I have been working on project with 8 Unisab and S7-400.
Communitcation with ProfiBus I use ProfiBus only for reading data from Unisab presure, temperature, current.....
When you buy Unisab they give you CD with documentation, GSD files and sample project in STEP7.
If I remember correctly have two type of GSD files based what you whant to read or send commands to Unisab.
If you can't find GSD I have it.