NMRA Digital Command Control Standard.pdf

Document History
This document is a direct translation of the Lenz document, v1.2, dated May 2012 in German. The German language is left in the document as the primary authority.

Overview
The document describes the Communications Standard for Digital Command Control Basic Decoder Transmission, applicable to all scales.

Physical Layer
General Information
The physical layer defines the communication protocol between the decoder and the RailCom detector.

RailCom – Transmitter in the Decoder
The decoder transmits data to the RailCom detector using a specific protocol.

The RailCom Detector
The RailCom detector receives data from the decoder and decodes it.

Timing
The timing of the communication protocol is defined.

Data Protection
Data protection mechanisms are implemented to prevent unauthorized access.

Packet Layer
RailCom Instruction Type MOB
The MOB instruction type is used for mobile decoders.

RailCom Instruction Type STAT
The STAT instruction type is used for stationary decoders.

RailCom Configuration Variables (CVs) and DCC-Instructions
System Requirements
The system requirements for RailCom are defined.

CVs
The CVs used for RailCom configuration are listed.

DCC Commands
System Commands
Additional Function Commands
Extended Programming Instructions
NOP for Accessory Decoders

Applications (Application/APP) Layer for Mobile Decoders
Programming on the Main (POM)
Read 1 Byte
Write 1 Byte
Write Bit
Read 4 Byte

ADR
EXT

RailCom Specification
Sending Local Information
Filling
DYN
subID

Application for Stationary Decoders (Switches, etc.)
SRQ
POM
Read 1 Byte
Write 1 Byte
Write Bit
Read 4 Byte
STAT1
TIME
ERROR
DYN
STAT2