EN 14908-2:2014

Open Data Communication in Building Automation, Controls and Building Management - Control Network Protocol - Part 2: Twisted Pair Communication

This European Standard specifies the control network protocol (CNP) free-topology twisted-pair channel for networked control systems in commercial Building Automation, Controls and Building Management and is used in conjunction with EN 14908-1:2014. The channel supports communication at 78,125 kbit/s between multiple nodes, each of which consists of a transceiver, a protocol processor, an application processor, a power supply, and application electronics.
This European Standard covers the complete physical layer (OSI Layer 1), including the interface to the Media Access Control (MAC) sub-layer and the interface to the medium. Parameters that are controlled by other layers but control the operation of the physical layer are also specified.

Offene Datenkommunikation für die Gebäudeautomation und Gebäudemanagement – Gebäude-Netzwerk-Protokoll — Teil 2: Kommunikation über verdrillte Zweidrahtleitungen

Réseau ouvert de communication de données pour l'automatisation, la régulation et la gestion technique du bâtiment - Protocole de contrôle du réseau - Partie 2 : Communication par paire torsadée

La présente Norme européenne, conjointement au prEN 14908-1:2012, spécifie le canal de communication sur paire torsadée à topologie libre du protocole de contrôle du réseau (CNP) destiné aux systèmes de contrôle en réseau en matière d'automatisation, de régulation et de gestion technique des bâtiments commerciaux. Ce canal prend en charge la communication à 78,125 kbps entre des noeuds multiples, chacun se composant d’un émetteur-récepteur, d’un processeur de protocole, d’un processeur d’application, d’une alimentation électrique et d’une électronique d’application.
La présente Norme européenne couvre la couche physique (couche 1 de l’OSI) dans son intégralité, incluant l’interface à la sous-couche contrôle d’accès au médium (MAC, Media Access Control) et l’interface au médium. Elle spécifie également les paramètres qui sont contrôlés par d’autres couches mais contrôlent le fonctionnement de la couche physique.

Odprta izmenjava podatkov v avtomatizaciji stavb in izvršnih elementov ter pri upravljanju stavb - Protokol regulacijske mreže - 2. del: Komunikacija zavitega para

Standard EN 14908-2 določa kanal zavitega para s poljubno topologijo protokola regulacijske mreže (CNP) za mrežne krmilne sisteme v komercialni avtomatizaciji stavb in izvršnih elementov ter pri upravljanju stavb in se uporablja v povezavi s standardom EN 14908-1:2014. Kanal podpira komunikacijo pri hitrosti 78.125 kbit/s med več vozlišči, vsako od teh pa sestavlja oddajno-sprejemna naprava, procesor protokola, procesor aplikacije, napajalnik in elektronika aplikacije. Ta evropski standard zajema celoten fizični sloj (OSI sloj 1), vključno s povezavo do podsloja krmiljenja dostopa do medija (MAC) in povezave do medija. Določeni so tudi parametri, ki nadzorujejo delovanje fizičnega sloja, vendar jih nadzorujejo drugi sloji.

General Information

• Status: Published
• Publication Date: 29-Apr-2014
• ICS: 35.240.67 - IT applications in building and construction industry
• ICS: 35.240.99 - IT applications in other fields
• ICS: 91.140.01 - Installations in buildings in general
• ICS: 97.120 - Automatic controls for household use
• Technical Committee: CEN/TC 247 - Controls for mechanical building services
• Drafting Committee: CEN/TC 247/WG 4 - Open System Data Transmission
• Current Stage: 9060 - Closure of 2 Year Review Enquiry - Review Enquiry
• Start Date: 02-Sep-2025
• Completion Date: 02-Sep-2025
• Mandate: M/490 - Standardisation mandate to the European Standardisation Organisations (ESOs) to support European Smart Grid deployment
• Ref Project: SIST EN 14908-2:2014 - Open Data Communication in Building Automation, Controls and Building Management - Control Network Protocol - Part 2: Twisted Pair Communication

Relations

• Replaces: EN 14908-2:2005 - Open Data Communication in Building Automation, Controls and Building Management - Control Network Protocol - Part 2: Twisted Pair Communication
• Effective Date: 07-May-2014

Overview

EN 14908-2:2014 specifies the Control Network Protocol (CNP) twisted‑pair channel for commercial building automation, controls and building management. It defines the complete OSI Layer 1 (physical layer) for a free‑topology two‑wire medium used together with EN 14908-1:2014 (protocol stack). The standard supports a data rate of 78.125 kbit/s, Differential Manchester encoding, and both locally powered and link‑powered nodes on the same segment.

Key topics and technical requirements

• Physical layer scope: interface to the MAC sub‑layer and the medium; termination, impedance and timing requirements.
• Data rate & encoding: 78.125 kbit/s using Differential Manchester (polarity‑insensitive).
• Topology support: free‑topology, bus, star, loop or any combination; bus segments are doubly terminated, free segments singly terminated.
• Node counts & distances:
  • Up to 128 link‑powered nodes or 64 locally‑powered nodes per segment (mixed configurations allowed subject to the standard’s constraints).
  • Maximum node‑to‑node distance: 250 m (free‑topology); maximum total wire length: 450 m.
  • Maximum bus length: 600 m (with 3 m max stub).
• Link power (power over the same two conductors):
  • Delivered via a passive coupler + power supply; differential DC output 41.0–42.4 VDC, nominal ±21 V with respect to earth.
  • Maximum steady‑state power draw per segment 36.5 W; output current capability 0–1.5 A DC.
  • Power supply requirements include start‑up behavior, short‑circuit recovery, output ripple (≤400 mV p‑p differential) and common‑mode noise (≤100 mV p‑p).
• Repeaters: allowed to interconnect segments; single repeater maximum in a path and repeater delay ≤ 36 µs.
• Cable: shall conform to EN 50173‑1 generic cabling requirements.
• Termination: specified RC terminations (values provided) for locally‑powered and link‑powered segments.

Applications

EN 14908-2:2014 is intended for implementation of reliable low‑speed control networks in commercial buildings, including:

• HVAC control networks
• Lighting and shade control
• Access control and security integration
• Distributed I/O and sensor/actuator networks
• Building Management Systems (BMS) where a standardized physical channel and optional link power are required

Who uses this standard

• Building automation system designers and integrators
• Control hardware manufacturers (transceivers, repeaters, power supplies)
• System installers and commissioning engineers
• Facility managers and BMS specifiers seeking interoperability

Related standards

• EN 14908-1:2014 - Protocol Stack (must be used in conjunction)
• EN 14908 Parts 3–6 (Power line channel, IP communication, Implementation, Application elements)
• EN 50173-1 - Generic cabling system requirements

Keywords: EN 14908-2:2014, Control Network Protocol, twisted pair communication, building automation, physical layer, link power, Differential Manchester, free‑topology.

Standards Content (Sample)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Odprta izmenjava podatkov v avtomatizaciji stavb in izvršnih elementov ter pri upravljanju stavb - Protokol regulacijske mreže - 2. del: Komunikacija zavitega paraFirmenneutrale Datenkommunikation für die Gebäudeautomation und Gebäudemanagement - Gebäudedatennetzprotokoll - Teil 2: Kommunikation über paarig verdrillte LeitungenRéseau ouvert de communication de données pour l'automatisation, la régulation et la gestion technique du bâtiment - Protocole de contrôle du réseau - Partie 2 : Communication par paire torsadéeOpen Data Communication in Building Automation, Controls and Building Management - Control Network Protocol - Part 2: Twisted Pair Communication97.120Avtomatske krmilne naprave za domAutomatic controls for household use35.240.99IT applications in other fieldsICS:Ta slovenski standard je istoveten z:EN 14908-2:2014SIST EN 14908-2:2014en,fr,de01-julij-2014SIST EN 14908-2:2014SLOVENSKI
STANDARDSIST EN 14908-2:20061DGRPHãþD

EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 14908-2
April 2014 ICS 35.240.99; 91.140.01; 97.120 Supersedes EN 14908-2:2005English Version
Open Data Communication in Building Automation, Controls and Building Management - Control Network Protocol - Part 2: Twisted Pair Communication
Réseau ouvert de communication de données pour l'automatisation, la régulation et la gestion technique du bâtiment - Protocole de contrôle du réseau - Partie 2 : Communication par paire torsadée
Offene Datenkommunikation für die Gebäudeautomation und Gebäudemanagement - Gebäude-Netzwerk-Protokoll
-Teil 2: Kommunikation über verdrillte Zweidrahtleitungen This European Standard was approved by CEN on 12 April 2013.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre:
Avenue Marnix 17,
B-1000 Brussels © 2014 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 14908-2:2014 ESIST EN 14908-2:2014

Foreword . 3 Introduction . 4 1 Scope . 5 2 Normative references . 5 3 Network overview . 5 4 System specifications . 5 4.1 General aspects . 5 4.2 Cable . 5 4.3 Topology . 5 4.3.1 Free or bus topology . 5 4.3.2 Repeater . 6 4.4 Cable termination. 6 4.4.1 Free-topology segment . 6 4.4.2 Bus topology segment . 6 4.5 Segment configuration . 6 4.6 Power specifications . 7 5 Link power . 7 5.1 General . 7 5.2 Source . 7 5.3 Power supply requirements . 8 5.4 Passive coupler circuit . 10 6 Node specifications . 12 6.1 Link power . 12 6.2 Hot plugging . 12 6.3 Transmitter/receiver interface to the MAC sub-layer . 12 6.3.1 Physical layer protocol data unit . 12 6.3.2 Frame format . 12 6.3.3 Transmit waveform . 13 6.4 Impedance . 15 7 Communication parameters . 16 Annex A (informative)
Environmental specifications . 18 Bibliography . 19 SIST EN 14908-2:2014

± 1 %, 1/8 W. The termination may be located anywhere on the segment. If the segment is link-powered, the termination shall be provided by the link power source. See Figure 5. The link power source and termination may be located anywhere on the segment. 4.4.2 Bus topology segment A bus topology segment shall have two terminations, one at each end of the bus. If the segment is locally powered, an RC network as shown in Figure 1 shall be used, with R1 = 105
± 1 %, 1/8 W at each end. If the segment is link-powered, the link power source shall provide one termination. See Figure 5. The other termination shall be an RC network as shown in Figure 1, with R1 = 105
1 %, 1/8 W.
Key 1 network connection Figure 1 — Terminatio
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