Update README.md

README.md

-# DO NOT USE THIS REPOSITORY
+# TOP LEVEL REPOSITORY FOR THE AIDA2020 TRIGGER LOGIC UNIT
+
+This repository is only used to provide the most up-to-date documentation for the AIDA2020 Trigger Logic Unit (TLU).
+
+The documentation is provided as a LaTex project. The file Main_TLU.pdf is a compiled PDF version of the documentation.
+
+## How to access the TLU software, hardware and firmware files
+
+The CAD design files for the TLU can be accessed via a dedicated hardware repository (https://ohwr.org/project/fmc-mtlu-hw/).
+
+Similarly, the firmware design files are stored in a 
 
 ## Use the repositories at https://ohwr.org/project/fmc-mtlu-gw/ ,  https://ohwr.org/project/fmc-mtlu-hw/ instead
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