# Theoretical question about CV's



## Brakeman Jake (Mar 8, 2009)

OK...it's a "what if" question that's come to my mind while tinkering with Decoder Pro.The way DP is designed,you can easily set all the CV's for a specific loco,read them to it's decoder and also store them for possible future resetting.Just great...

Then the same settings can be written to another similar loco/decoder setup and obtain similar performance.Even better.But,if one was to write the same settings to a different loco/decoder setup,one could expect it will run though with may be slight differences in performance...is my theory right?

But,what if such a preset sheat was written to a decoder that doesn't use all the preset CV's,like let's say preset steam sound CV's to a regular diesel that has no sound at all.Would the decoder accept only the CV's it needs and ignore the extra ones or would it get messed up by the useless data?My example is extreme I know and my theory is that the excess CV's wouldn't get written at all but what if they did?


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## Rangerover (Feb 8, 2012)

Jake, I too thought about this using JMRI but there are many other CV's that control how a locomotive performs, but not all decoders use all CV's. Often, different DCC manufacturers use different CV numbers for the more advanced decoder features. The most common CV's that manufacturer's use in compliance with NMRA standards and is mandatory is CV-1 the primary address, CV-7 manufacture version, CV-8 manufacture ID, CV-29 cnfiguration data, after that all bets are off that the other cv's that are used to control the loco decoder, use the same cv or value. The only way I have done this is if I used the same decoder in a different loco as you describe, and write the changes to the new decoder as a starting point. 

LOL, thank God for factory reset!!!!!!!! Jim


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## Rangerover (Feb 8, 2012)

Jake if you tried to write changes from for instance a Digitrax DZ143PS to an NCE D13SR decoder which have basically the same functions but with different performance, I would think using JMRI you would get an ERROR message and it wouldn't write. Just my opinion! Jim


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## NIMT (Jan 6, 2011)

Decoders CV have been designed to be semi universal, Most if not all decoders CV can be programed the same without doing a bit of harm to it.
I use a standard set of CV's for all my diesel units and another set for all my steam units regardless of the decoder.
There are additional CV values to sound decoders over standard decoders.
JMRI is a much simpler and safer way to change CV's of a decoder, if you read or input the proper decoder it's near to impossible to set CV's that the decoder will not understand or has no use for. It also goes the same way for you missing the CV's that you should have changed.
90% of all the calls I get involves not understanding CV's or how to change them! JMRI works being an excellent translation program, you tell it English and it spits out CV!


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