CV-Calc

DCC CV - Configuration Variables

Every DCC decoder can be programmed to respond to a specific direction. Loco decoders also can be programmed to use 14, 28 or 128 speed steps, acceleration delay, braking delay, etc. Accesory decoders can change the time of output activation. The features are stored in special locations of internal decoder memory. These locations are called Configuration Variables or simply CV.

CV programming is done from Command Station in diferent modes of programming (direct, register, paged, PoM) not all decoders accept all programming modes so you have to check it in the decoder manual.

The main accepted CV for most loco and function decoders are:

CV1

Decoder address (1 .. 127)

CV2

Starting Voltage

CV3

Acceleration delay

CV4

Deceleration delay

CV5

Maximum speed

CV7

Decoder Version (only read)

CV8

Manufacturer ID (only read)

CV17-CV18

Extended address (1 .. 16383). Have to be programmed in a special way:

Address
CV17
CV18

CV19

Multi unit (consist) address

CV29

Decoder Configuration
This is calculated from its bits
Bit 0 -> 0: Direction normal, 1: Direction inverted
Bit 1 -> 0: 14 speed steps, 1: 28 / 128 speed steps
Bit 2 -> 0: Only DCC, 1: DCC and DC
Bit 3 -> 0: RailCom off, 1: RailCom on
Bit 4 -> 0: Factory preset speed curve, 1: User speed curve
Bit 5 -> 0: Address in CV1, 1: Address in CV17-CV18

CV29

For Accesory decoders the main CV used are:

CV513 Decoder Address (low byte)
Address is between 1 .. 512 and controls four outputs (2048 in total)

Address

CV513

CV521

Outputs

CV514 Auxiliary Activation (a 1 in a bit actives corresponding output)

CV515-CV518 Output activation time

CV519 Decoder Version (only read)

CV520 Manufactured ID (only read)

CV521 Decoder address (high byte)