The process to downgrade the software version of Abacus is exactly the same as upgrade. Followings are the steps:-
1. Download the Abacus GUI software from the CSC web site.
2. Install the software in the PC.
3. Run the GUI software.
4. "Upgrade" the firmware of the Abacus. (Detail to upgrade the firmware can be found in the Abacus Software Manual).
Done.