Not sure if this helps and I know its about Digitrax Decoders but I found this at least explained function mapping pretty well. FUNCTION MAPPING The idea is basically to take the value of one CV or the CV controlling say F4 and program that value into F3 and program a new value into F4 or a value of 0 which would mean into controls nothing. Anyway, it is confusing and it took me a while to get it right. I took a look on the MRC website and I didnt see anything about function mapping so im not sure exactly how this works with their decoders. Hope this helps a little anyway.
Don
I am new to the DCC world so this may have been asked and answered already. I have a digitrax zephyr and just installed a MRC 1802 decoder in a SD-40. Everything seams to be working, the problem is that F3 is supposed to control the coupling sound and the MRC decoder has it assigned to F4. I read the manual about remapping but do not quite get it. Any help would be appreciated.