Summary: Multifunction Decoders have a default address of 3 as per the NMRA standard.
The Default Address is the Primary address specified in the NMRA DCC Standards for retail multifunction decoders. Manufacturers are required to set the default address to 3 (three). There are no leading zeros on the address.
- The default address only applies to multifunction decoders sold at retail. OEM decoders installed in a locomotive can be set to any address the manufacturer wishes to use.
If you reset your multifunction decoder, all the Configuration Variables will be restored to their factory default values, including the address. Any new locomotive will respond to address three providing it has a decoder installed and no programming has been done. While the manufacturer of the locomotive can set its decoder's address to any value, it usually is 3. The NMRA DCC Standards specifies a retail multifunction decoder use a primary address of 3.
By specifying a default value of three in CV 1, anyone can acquire a decoder with factory default values and either operate the locomotive, or program it. This is necessary for a new decoder, or one that has been reset to factory values, so that the user doesn't have to sift through documentation for that decoder (providing you know who made it and what the product name/family is!) to figure out how to address it.
After a decoder reset, the Primary Address is set to 3 in CV1. Any Extended Addresses have been reset and their CVs cleared. Configuration Register CV29 is also set to its default value, clearing the Extended Address Mode bit.