DCC Info
CV 29 - Configuration Data


Entering invalid values will result in "ERR" being shown in the "CV 29 Value" field.

To Determine Settings for a Given Value

Enter a numeric value from 0 to 255 in the "CV 29 Value" field, then click the "Show Settings for Value -->" button.

To Determine Value for Given Settings

Check the desired checkboxes under the "CV 29 Settings" heading, then click the "<-- Show Value for Settings" button.

CV 29 Value Calculation CV 29 Settings
  (0 - 255)

Locomotive Direction
Speed Steps
DC Operation
2-Way Communications (RailCom)
Speed Table
Short v. Long Addressing

Bit Decimal
Name Description
0 1 Locomotive Direction "0" = normal, "1" = reversed. This bit controls the locomotive's forward and backward direction when operating on DCC (not when operating on DC-powered track). Directional sensitive functions, such as headlights (FL and FR), will also be reversed so that they line up with the locomotive's new forward direction.
  • 0 (off) = directions of travel are normal
  • 1 (on) = directions of travel are reversed
(See RP-9.1.1 for more information.)
1 2 Speed Steps Selectes between 14 speed steps and 28/128 speed steps. In the early days of DCC, 14 speed steps was the maximum number supported by many decoders. Today nearly all decoders support 28/128 speed steps, which is the option preferred by most operators.
  • 0 (off) = 14 speed steps
  • 1 (on) = 28/128 speed steps
(See RP-9.2.1 for more information.)
2 4 DC Operation Some decoders are capable of sensing whether they are on track powered by DC and, if so, behave like a locomotive running without a DCC decoder.
  • 0 (off) = disable use on DC-powered track
  • 1 (on) = enables use on DC-powered track
(See CV 12 for more information.)
3 8 2-Way Communications
Use of this value is under formal review by the DCC Working Group but has not been approved by the Working Group, the General Technical Committee or approved by the Board of Trustees.

(See RP-9.3.2 for more information.)
4 16 Speed Table Two speed tables are available to locomotives. One is controled by CV 2 (speed step 1 voltage), CV 6 (mid speed step voltage) and CV 5 (highest speed step voltage). The other is controlled by values in CVs 66 (lowest speed step voltage) through 95 (highest speed step voltage).
  • 0 (off) = CVs 2, 5 & 6
  • 1 (on) = CVs 66 - 99
5 32 Short v. Long Addressing Most decoders support the use of short addresses (with values between 1 and 127) and long addresses (with values between 1 and 9999). The short address is stored in CV 1 and the long address is stored in CVs 17 & 18. This setting indicates whether the decoder should respond to commands sent to the short address or the long address.
  • 0 (off) = respond to short address
  • 1 (on) = respond to long address
(See RP-9.2.1 for more information.)
6 64 Reserved Reserved for future use.
7 128 Reserved Reserved for future use.


  • NMRA RP 9.2.2 (July 2007)