This is the main link:
http://wiki.ross-tech.com/index.php/VW_Radio/Navigation_System
For the RCD-510 here are the options which (should) exist in the long coding for the radio (in bold options enabled for my car which has RCD-510 and MDI):
Radio Configuration
-AUX-IN Access restricted
-CD-Changer/iPod/USB Connection Monitoring active
-AUX-IN Connection Monitoring active
-Parking Aid installed
-Shortpress Steering Wheel Buttons installed
-Telephone OR Telephone Preparation (CAN) installed
-Back-Up Camera installed
Sound System Correction
-Sound System not installed
-Volkswagen Sound System (DDP DSP)
-Skoda Soundsystem (CAN DSP)
-Dynaudio Sound System (DDP DSP)
-Volkswagen Sound System (BAP DSP)
-Dynaudio Sound System (BAP DSP)
Speaker Channels
-Sound System (active Speakers)
-2 Speaker Channels (2 passive Front Speakers)
-4 Speaker Channels (2 passive Speakers each Front and Rear)
Treble Speaker Monitoring
-Treble Speaker Monitoring deactivated (Sound System)
-Treble Speaker Monitoring for Front Speakers active
-Treble Speaker Monitoring for Rear Speakers active
-Treble Speaker Monitoring for Front & Rear Speakers active
PM me if you need anymore info. And use the link above to find your radio if it's a different model than yours.