CV means Configuration Variable

CV01

Early on, decoders only had one byte of data (CV 1) for the address. It was decided that addresses from 00 to 127 would be defined by this byte of data. This leads to lots of confusion, like why is 120 a “two-digit" address? Because it is pseudo hexadecimal - now are you not sorry you asked? Do not worry about why, just know what. Best to call it a SHORT address.

Different manufacturers define 2-digit (short) and 4-digit (long) differently, all within the NMRA standard. Lenz defines any number larger than 99 as a long. Digitrax defines numbers larger than 127 as long. NCE lets you decide (0120 is a long address, while 120 is short).

So, if you are trying to address a loco with numbers between 100 and 127, you need to spend a bit of time thinking about it. If you only run on one system or only on NCE and Digitrax, fine - just program the loco address you want to use as a short address - CV01. If you are going with Lenz only, they handle it automatically. If you, like me, have locos to run on different systems which are numbered between 100 and 127, YIKES, it i’s a mess! For awhile, I addressed my Santa Fe FT Cat’s Whisker ABBA set as 27, instead of fighting with 127! Since then I've renumbered it 134 - a SAFE long address.

CV02

First off, this CV is misnamed - it is frequently called START VOLTAGE. The voltage on the motor is constant at about the track voltage. CV 02 adjusts the amount of time that the voltage is applied to the motor at speed step one. I like to set it so that the loco just creeps - assuming you are not using BEMF. (BEMF decoders should auto adjust for this, so CV02 should be set to zero). Tsunami decoders should have this CV set to zero unless BEMF is totally disabled. To set start speed on a Tsunami, CLICK HERE.

Here’s how to set CV 02

1. Set the loco to speed step 01
2. Set CV 02 = 001
3. See if the loco moves. If so, stop
4. If not, add 1 to the value of CV 02, then go to step 3.

Then Bruce likes to set CV 05 and 06. See below.

CV05

CV 05 sets the top speed the loco can run. You can adjust this so that the loco runs no faster than your desired top speed. Scale speeds of 40 to 90 MPH are reasonable. Frequently setting this to zero will have the decoder run the loco as fast as it is physically capable of running.

CV06

CV 06 sets the midpoint speed the loco can run. Once I have set the maximum speed (CV05), I use the same loop to set the speed of the loco at a midpoint throttle setting. Frequently setting this to zero will have the decoder calculate the midpoint for you.

CV17-18

When 4-digit addressing (actually any address above 127) was implemented, the NMRA standard included some very complex calculations. It is not simply putting two digits in one CV and the other two in another. Setting these CVs is very involved. Bruce recommends that you use some program, like DecoderPro to accomplish this task. If you don't haveDecoderPro, you can use the calculator provided by The 2 mm Scale Association - CLICK HERE.

CV29

CV 29 sets the overall personality of the loco: whether it runs on DC or not, is the normal direction of travel forward or reversed, etc. Setting this CV is very involved. Bruce recommends that you use some program, like DecoderProto accomplish this task. If you don't have DecoderPro, you can use the calculator provided by The 2 mm Scale Association - CLICK HERE.

If you want to roll your own, CLICK HERE for a little sheet I built for you to print and fill in personally.

Copyright © Bruce F. Petrarca 2007 - 2017; All Rights Reserved