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Locomotive addresses

Both locomotive and function decoder have a fundamentally different address scheme compared to accessory decoder.

They have an individual address, which is unique on the model installation. An exception are carriage decoder of a train for example, which are set to the same address.

There are two pays of setting the address in the DCC protocol.

  • There is the short address (as CV 2), that may contain values between 1 and 127.
    In principle the CV can contain 255 values, however the encoding of the commands uses the most significant bit for other purposes. Thus there are only 127 different addresses. The address 0 can not be used. It is used as so called 'broadcast' address, which all decoders respond to.
  • In case an address above 127 should be used, the extended or long address, which allows values up to 10239, must be utilized. This address is stored in the CVs 17 and 18.

In CV 29 is stored which address method is used for the decoder.

Each decoder is addressed with an address in the Märklin/Motorola format. For decoder that support both protocols, the first DCC locomotive address is used.

The composite address

Especially older systems use the so-called composite, in which various decoder are combined with an additional address. This is especially useful when using multiple motor vehicles in one train. It allows to control all together, instead of each one separately. Modern controller offer different possibilities for the common control of decoder. Nevertheless the composite control is still justified.

The standard only provides a short address, which is set in CV 19. In addition, CV 19 contains information whether the locomotive changes direction or not. The effects are explained in direction of travel.

Locomotive address of Qdecoder

Qdecoder of the all-in-one class offer up to four locomotive addresses to support the evaluation of Qfunctions. The composite address is not evaluated by the Qfunctions. The addresses are stored in the configuration variables 288/289 (second address), 290/291 and 292/293.

The function outputs of the Qdecoder can also be switched directly via the function keys of the locomotive control

Qdecoder support the full address range of DDC-locomotive addresses and Märklin/Motorola locomotive addresses in the usual range between 1 and 80.

Construction of the long locomotive address and the configuration variables

CV 29 contains a number of basic settings. Bit 6 is used to distinguish between short and long address. If it is set, long addresses will be used, if not, then the short address is valid.

The distribution of long addresses in CVs 17 and 18 is fairly crude. For that reason, modern controller do the programming automatically and manage the bit in CV 29 at the same time. The CV 18 contain the least significant part of the address, CV 17 the most significant one. To complicate things further, the most significant part of the long address contains an offset of 192.
CV 17 = decoder address / 256 + 192
For addresses less than 256, CV 17 always contains the value '192'; for addresses between 256 and 511 always '193', and so on.
CV 18 = remainder of the division decoder address / 256.          

For addresses less than 256, CV 18 has the value of the address; for addresses between 256 and 511 the address - 256 and so on.

By default, all decoders of all manufacturers are pre programmed to the short address 3. It is therefore required for all new decoder to change the decoder address. The CVs for the addressing are:

CV address Bit number Default CV value Description
29 6 0 Selection between short and long locomotive address.
  • If the bit has the value 0, the short address is used.
  • If the bit has the value 1, the long address is used.
(Note: The bites are numbered 0 to 7, with bit 0 at the very 'right').
1 6 to 0 3 short locomotive address
17 192 long locomotive address (most significant part)
18 3 long locomotive address (least significant part)
19 6 to 0 0 Composite address
Additional (short) locomotive address that the decoder reacts to. If CV19 has the value 0, no composite address is active.
7 0 Composite direction
  • If the bit has the value 0, the vehicle travels in the same direction as the composite.
  • If the bit has the value 1, the vehicle travels in the opposite direction.

For accessory decoder the standard assigns CV address 29 for other purposes. Please use address 59 instead of address 29.


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