DCC Function mapping - Easy to understand tutorial 

To have the right lights turned on when you press a Function key on your digital train controller with your new digital decoder, you will most likely have to dive into Function mapping. This tutorial will make you understand how it works, how you can find out what light function is connected to which F key and how you can change it to the way you prefer it.
Please note that the given CV settings are for Train-O-Matic decoders only. Train-O-Matic gives you forward and reverse on F1, I haven't seen this on other decoders. Zimo also starts at CV33 with F0, but because they only have F1 in one direction, their CV settings end one CV earlier than Train-O-Matic. So check with the manual of your decoder if used with another decoder than Train-O-Matic what the CVs are to connect the F keys to the outputs.
You can purchase Train-O-Matic decoders from the Tramfabriek here: tramfabriek.co....