CV Access  

On programmable decoders the characteristics are defined by Configuration Variables (CVs or Registers). All of the data pertaining to the behavior of the locomotive is stored in these CVs. The significance of individual registers depends on the manufacturer and the decoder. Changes in registers can have far-reaching consequences up to and including the locomotive becoming totally unusable. Changes are written immediately in the decoders – there is no undo function in order to go back to the previous settings.
The settings in the registers should only be handled by experienced users and after studying the locomotive or decoder instructions.
 

Go to Configuration for a Locomotive with a  DCC-Decoder  
Go to Changing Configuration Variables in the Decoder