What the heck is a CV?

[CAT345C]

Okay guys, I am new to DCC so I basically know that I put decoders in a choo choo and it will move when I program an address. I'm at the point now where I want to start speed matching engines, adjusting bell and horn sounds and seeing what this system can really do. My question is, are CV's uniform in the industry for the most part? For example, is a CV30 on a NCE decoder going to be the same as CV30 on the factory equipped Broadway limited unit that I have?

Does anybody recommend any books on DCC?

For what its worth, I picked up the NCE Power Cab, so far I love the thing, and already made plans to expand to the bigger booster and wireless.

[GP9R]

I would suggest picking up a locobuffer. It'll let you use your computer to do programming in an easy to read/work table

[SD80MAC]

CV's are NOT uniform throughout the industry, and can even vary between different decoders made by the same company.

[fmilhaupt]

I would suggest picking up a locobuffer. It'll let you use your computer to do programming in an easy to read/work table

A computer interface is definitely a good idea, but since he has an NCE PowerCab, a Locobuffer (a Loconet/Digitrax-only product) won't do him much good. An NCE USB interface would be the ticket.

To elaborate a bit on what SD80MAC said, there are certain basic CVs that are standard among the DCC decoder manufacturers, but once you get beyond the basic CVs, the manufacturers can and do go just about anywhere. The sound decoder manufacturers are the worst for that.

The only CVs that are required to be supported by all DCC-compatible decoders are:

CV1 - 2-digit short address
CV7 - Decoder model ID code (some manufacturers aren't very good about making this different for their different decoder models)
CV8 - Manufacturer ID code (assigned by the NMRA)
CV29 - Addressing type, base direction, use of custom speed table, ability to operate on analog DC power

Most current full-featured decoders support at least the following CVs, too:

CV2 - Starting voltage level
CV3 - Acceleration rate
CV4 - Deceleration rate
CV5 - Maximum voltage level
CV6 - Middle voltage level
CV15/16 - Decoder selection and lock for locomotives with more than one decoder installed
CV17/CV18 - 4-digit locomotive address
CV19 - MU consist address for decoder-assisted ("Advanced") consisting
CV67-94: Customizable speed curve table

Since these definitions were developed over a period of years, it is possible to find older decoders for sale that do not support some of these CVs. Especially when someone is clearing out old inventory or selling off old decoders they've replaced with something newer (I've done that at train shows a few times over the years).

When you get into things like controlling the different lighting outputs on a decoder, the manufacturers are all over the map on where you program things such as whether a light comes on automatically in forward or reverse. For example, on a Digitrax decoder, you program CV49 and CV50 to determine how the front and rear headlights behave. On an NCE decoder, you program CV120 and CV121. And the different manufacturers use different values in these CVs to mean the same thing.

You pretty much have to refer to each manufacturer's decoder documentation to see how their decoders are set up. The easiest way to handle all of this is to do what GP9R said and get a computer interface and a software package like JMRI (which happens to be available free) to handle the CV-twiddling for you. Digitrax, EasyDCC, Lenz, NCE, Zimo and a few others are supported by JMRI. MRC's DCC system has its own software for programming decoders, but it doesn't have most of the useful features JMRI has.

[GP9R]

I would suggest picking up a locobuffer. It'll let you use your computer to do programming in an easy to read/work table

A computer interface is definitely a good idea, but since he has an NCE PowerCab, a Locobuffer (a Loconet/Digitrax-only product) won't do him much good. An NCE USB interface would be the ticket.

To elaborate a bit on what SD80MAC said, there are certain basic CVs that are standard among the DCC decoder manufacturers, but once you get beyond the basic CVs, the manufacturers can and do go just about anywhere. The sound decoder manufacturers are the worst for that.

The only CVs that are required to be supported by all DCC-compatible decoders are:

CV1 - 2-digit short address
CV7 - Decoder model ID code (some manufacturers aren't very good about making this different for their different decoder models)
CV8 - Manufacturer ID code (assigned by the NMRA)
CV29 - Addressing type, base direction, use of custom speed table, ability to operate on analog DC power

Most current full-featured decoders support at least the following CVs, too:

CV2 - Starting voltage level
CV3 - Acceleration rate
CV4 - Deceleration rate
CV5 - Maximum voltage level
CV6 - Middle voltage level
CV15/16 - Decoder selection and lock for locomotives with more than one decoder installed
CV17/CV18 - 4-digit locomotive address
CV19 - MU consist address for decoder-assisted ("Advanced") consisting
CV67-94: Customizable speed curve table

Since these definitions were developed over a period of years, it is possible to find older decoders for sale that do not support some of these CVs. Especially when someone is clearing out old inventory or selling off old decoders they've replaced with something newer (I've done that at train shows a few times over the years).

When you get into things like controlling the different lighting outputs on a decoder, the manufacturers are all over the map on where you program things such as whether a light comes on automatically in forward or reverse. For example, on a Digitrax decoder, you program CV49 and CV50 to determine how the front and rear headlights behave. On an NCE decoder, you program CV120 and CV121. And the different manufacturers use different values in these CVs to mean the same thing.

You pretty much have to refer to each manufacturer's decoder documentation to see how their decoders are set up. The easiest way to handle all of this is to do what GP9R said and get a computer interface and a software package like JMRI (which happens to be available free) to handle the CV-twiddling for you. Digitrax, EasyDCC, Lenz, NCE, Zimo and a few others are supported by JMRI. MRC's DCC system has its own software for programming decoders, but it doesn't have most of the useful features JMRI has.

I was not aware that the locobuffer was digitrax specific. Ya learn something every day

[CAT345C]

Thanks for all the great information guys. I must ask skippy a question about this system everyday and Im pretty sure I've just about driven him nuts. I've got JMRI on my computer and I know there was a way to use Decoder pro to program locomotives, I just wasn't aware of the complexity of CV's and what not that I would be getting into. I'll have to pickup one of the USB interface's from G&G Trains next time I'm down there.

Thanks!

Cletus OUT

[Hugh]

I use a Sprog II to work with DecoderPro.