Programming 101–Basic CVs
CVs 1, 2, 3, 4, 5, 6, and 29 are the basic CVs that most folks might want to program using a throttle. Once you get above these you really are better off using DecoderPro or LokProgrammer. This is also true for CV29 but I will show you what it does anyway in the second part of this post.
CV 1 is the two digit address. It is pretty straightforward, just enter the address and hit enter and you’re done. However with the near universal availability of four digit addresses most folks don’t use this very much anymore. It can come in handy for industrial switcher locomotives and the occasional one or two digit oddball–for example I have an RS11 no. 11.
CV 2 is the initial voltage adjuster. It helps get the locomotive moving as soon as you open the throttle to speed step 1 by adjusti g the voltage to the motor. It also serves as the first setting in a three step speed curve used in speed matching–more on that in a bit. For this one just keep nudging the value up until the locomotive just begins to crawl when you open the throttle a crack. Note though that some decoders also have other CV settings that give an extra nudge at low speed settings to help overcome stiction, so check your manuals.
CVs 3 & 4 are the acceleration and deceleration momentum settings, respectively. These settings slow down acceleration and deceleration rates to help simulate the tendency of prototype locomotives to accelerate and decelerate slowly due to their heavy weight and the weight of the load they are pulling. Some decoders factor this into their other operations so you need to factor that into any changes you make. For example on LokSound decoders the deceleration rate affects how much brake sound you will hear.
CVs 5 & 6 are the top and midpoint speed settings, respectively, for a three step speed curve–CV2 is the minimum speed step setting. To speed match locomotives you set the top and bottom settings and finally adjust the midpoint setting to get two locomotives to operate at the same speeds across the throttle range. See my previous post and video on speed matching for more on this process.
CV29 is often called the master CV since it controls several features. Calculating a value for CV29 is complex enough that some programming throttles and command stations do it for you based on your input. Digitrax has a table of common values in their decoder manual making it easier to understand this CV. Because of its complexity I will cover it later.