CV29 Bit Functions Chart
Bit Value Description
0 1 Controls normal direction of travel (ON to reverse)
1 2 OFF for 14 speed steps, ON for 28 speed steps
2 4 OFF will not run on DC power, ON to run on DC power
3 8 ON for advance acknowledgment
4 16 OFF for standard speed table. ON for alternate table (CV67-94)
5 32 OFF for 2-digit addressing. ON for 4-digit addressing
6 64 Reserved for future use by NMRA
7 128 OFF for multi-function decoder (Loco, etc.). ON for accessory decoder.
The chart above is an aid in determining the proper number to input to CV29 based on the settings you desire.
If, for example, you want to have 28 speed steps you would input 002. If you wanted 28 speed steps and wanted 4-digit addresses (loco number), you would add the 2 (for 28 speed steps) to 32 (for 4-digit addressing) and input the total 34.
If you wanted the loco to always run in the opposite direction to what the throttle sends (e.g. back-to-back F-unit consist), you would add 1 to the number for the reverse-running loco and input the new total 35.
Another example: A loco running on 14 speed steps, 2-digit addressing, standard speed table and normal direction of travel would usually have a CV value of 0 (zero). If you wished to run this DCC-equipped loco on someone else’s layout that was DC, you would change CV29 to 4 (the Bit 2 value) before you left home. If you wanted the same loco to run on 28 speed steps when running in DCC, you would add the 2 to the 4 and enter 6 in CV29.
The numbers in the “Value” column for each feature you wish to turn “ON” are added together to determine the correct value to input to CV29.
If CV29 for a loco decoder has a value of 0 then each feature is turned off:
Normally you would NEVER add the 64 for bit 6 or the 8 for bit 3. Bit 7 (value 128) is only used to identify an accessory decoder and any DCC loco that you only run at home or on another DCC layout would never have bit 2 (Value 4) added to the CV29 value you input. In fact, under ordinary circumstances, the programming takes care of setting CV29. When you first get a decoder (in a loco or one to add to a DC loco) the CV29 value will likely be set to 0. Remember, decoders are set to the address 03 (a 2-digit address), so bit 5 can be set to either 0 or 32. If it is set to 32, a 2-digit address will work fine as 0003 or 03 would both call up the loco.
Even if bit 5 is set to 0 for a new decoder, setting a 4-digit address with the throttle will automatically reset CV29 in most, if not all, new decoders. Bit 4 (Value 16) will only be turned on if you decide that the loco doesn’t work well in a consist with another loco. If you attempt to consist Loco B with “lead” Loco A and they are push-pulling each other you need to take steps to match their acceleration, deceleration, and constant speeds. Sometimes you can luck out and find that one of the “speed tables” stored in your decoder will match Loco B to Loco A. But, even then, it’s not likely to get the near-perfect match required for smooth running. If you can’t find a satisfactory alternate speed table from those supplied by the decoder, you will need to undertake the tedious task of inputting a manual speed table. There are 28 CV’s (to match 28 speed steps) from CV67 – CV94 where you place the values that set the speed for each of 28 speed steps.
See “T & T – Speed Matching” for detailed instructions at link below:
https://trainops.wordpress.com/tips-techniques/t-t-speed-table/
Model Train Operations 