Home and Building Electronic Systems (HBES) Part 5-2: Media and media dependent layers - Network based on HBES Class 1, Twisted Pair

This European Standard defines the mandatory and optional requirements for the medium specific physical and data link layer for HBES Class 1 Twisted Pair TP1. Data link layer interface and general definitions, which are media independent, are given in EN 50090 4 2.

Elektrische Systemtechnik für Heim und Gebäude (ESHG) - Teil 5-2: Medien und medienabhängige Schichten - Netzwerk basierend auf ESHG Klasse 1, Twisted Pair

Systèmes électroniques pour les foyers domestiques et les bâtiments (HBES) - Partie 5-2: Médias et couches dépendantes des médias - Réseau fondé sur HBES Classe 1, Paire torsadée

Le présent document définit les exigences obligatoires et facultatives relatives à la couche physique et de liaison des données spécifiques à un média, pour les HBES de classe 1 Paire torsadée TP1. Les définitions de l'interface de la couche liaison de données ainsi que les définitions générales, qui sont indépendantes des médias, sont données dans l'EN 50090 4 2.

Stanovanjski in stavbni elektronski sistemi (HBES) - 5-2. del: Mediji in nivoji, odvisni od medijev - Omrežja, ki temeljijo na HBES razreda 1, zviti par

General Information

Status
Published
Publication Date
09-Apr-2020
Current Stage
6060 - Document made available
Due Date
10-Apr-2020
Completion Date
10-Apr-2020

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SLOVENSKI STANDARD
SIST EN 50090-5-2:2020
01-junij-2020
Nadomešča:
SIST EN 50090-5-2:2005
Stanovanjski in stavbni elektronski sistemi (HBES) - 5-2. del: Mediji in nivoji,
odvisni od medijev - Omrežja, ki temeljijo na HBES razreda 1, zviti par
Home and Building Electronic Systems (HBES) Part 5-2: Media and media dependent
layers - Network based on HBES Class 1, Twisted Pair
Elektrische Systemtechnik für Heim und Gebäude (ESHG) - Teil 5-2: Medien und
medienabhängige Schichten - Netzwerk basierend auf ESHG Klasse 1, Twisted Pair

Systèmes électroniques pour les foyers domestiques et les bâtiments (HBES) - Partie 5-

2: Medias et couches dépendantes des medias - Réseau basé sur HBES Classe 1,
Paire Torsadée
Ta slovenski standard je istoveten z: EN 50090-5-2:2020
ICS:
35.240.67 Uporabniške rešitve IT v IT applications in building
gradbeništvu and construction industry
97.120 Avtomatske krmilne naprave Automatic controls for
za dom household use
SIST EN 50090-5-2:2020 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST EN 50090-5-2:2020
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SIST EN 50090-5-2:2020
EUROPEAN STANDARD EN 50090-5-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
April 2020
ICS 35.100.20; 97.120; 35.100.10 Supersedes EN 50090-5-2:2004 and all of its
amendments and corrigenda (if any)
English Version
Home and Building Electronic Systems (HBES) Part 5-2: Media
and media dependent layers - Network based on HBES Class 1,
Twisted Pair

Systèmes électroniques pour les foyers domestiques et les Elektrische Systemtechnik für Heim und Gebäude (ESHG) -

bâtiments (HBES) - Partie 5-2: Medias et couches Teil 5-2: Medien und medienabhängige Schichten -

dépendantes des medias - Réseau basé sur HBES Classe Netzwerk basierend auf ESHG Klasse 1, Twisted Pair

1, Paire Torsadée

This European Standard was approved by CENELEC on 2020-01-09. CENELEC 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 CENELEC 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 CENELEC member into its own language and notified to the CEN-CENELEC Management Centre has the

same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,

Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the

Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2020 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.

Ref. No. EN 50090-5-2:2020 E
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SIST EN 50090-5-2:2020
EN 50090-5-2:2020 (E)
Contents

European foreword ................................................................................................................. 4

Introduction............................................................................................................................. 5

1 Scope ............................................................................................................................... 6

2 Normative references ....................................................................................................... 6

3 Terms, definitions and abbreviations ................................................................................ 7

3.1 Terms and definitions .............................................................................................. 7

3.2 Abbreviations .......................................................................................................... 8

4 Requirements for HBES Class 1, Twisted Pair Type 1 (TP1-64 and TP1-256) .................. 9

4.1 Physical layer requirements – Overview .................................................................. 9

4.2 Requirements for analogue bus signals ................................................................. 12

4.2.1 General ..................................................................................................... 12

4.2.2 Specification of logical “1” ......................................................................... 12

4.2.3 Specification of logical “0” (Single) ............................................................ 13

4.2.4 Specification of logical “0” (overlapping) .................................................... 14

4.2.5 Analogue requirements within a transmitted character ............................... 15

4.2.6 Simultaneous sending / collision behaviour ................................................ 16

4.3 Medium attachment unit (MAU) ............................................................................. 16

4.3.1 General ..................................................................................................... 16

4.3.2 Requirements within a physical segment ................................................... 16

4.3.3 Remote powered devices (RPD) ................................................................ 24

4.4 Twisted Pair Type 1 bus cable ............................................................................... 25

4.4.1 Requirements ............................................................................................ 25

4.4.2 Measurement of continuous magnetic and electrical interference

respectively transient induced differential voltages .................................... 26

4.5 Topology ............................................................................................................... 27

4.5.1 Physical segment ..................................................................................... 27

4.5.2 Bridge ....................................................................................................... 27

4.5.3 Router, subline, main line and zone ........................................................... 28

4.5.4 Gateways to other networks ...................................................................... 29

4.6 Services of the physical layer type Twisted Pair Type 1 ......................................... 30

4.6.1 General ..................................................................................................... 30

4.6.2 Physical_Data service ............................................................................... 30

4.6.3 Physical_Reset service .............................................................................. 32

4.7 Behaviour of the physical layer type Twisted Pair Type 1 entity ............................. 32

4.8 Data link layer type Twisted Pair Type 1 ................................................................ 32

4.8.1 General ..................................................................................................... 32

4.8.2 Frame formats ........................................................................................... 33

4.8.3 Medium access control .............................................................................. 38

4.8.4 Data link layer services ............................................................................. 41

4.8.5 Data link layer protocol .............................................................................. 44

4.8.6 State machine of data link layer ................................................................. 46

4.8.7 Parameters of data link layer ..................................................................... 46

4.8.8 Reflections on the system behaviour in case of L_Poll_Data

configuration faults .................................................................................... 47

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EN 50090-5-2:2020 (E)

4.8.9 The data link layer of a bridge ................................................................... 47

4.8.10 The data link layer of a router .................................................................... 47

4.8.11 Externally accessible bus monitor and data link layer interface .................. 47

Bibliography .......................................................................................................................... 48

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SIST EN 50090-5-2:2020
EN 50090-5-2:2020 (E)
European foreword

This document (EN 50090-5-2:2020) has been prepared by CLC/TC 205, “Home and Building Electronic

Systems (HBES)”
The following dates are fixed:
• latest date by which this document has (dop) 2020-10-10
to be implemented at national level by
publication of an identical national
standard or by endorsement
• latest date by which the national (dow) 2023-04-10
standards conflicting with this document
have to be withdrawn

This document will supersede EN 50090-5-2:2004 and all of its amendments and corrigenda (if any).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.

EN 50090-5-2 is part of the EN 50090 series of European Standards, which will comprise the following

parts:
— Part 1: Standardization structure;
— Part 3: Aspects of application;
— Part 4: Media independent layers;
— Part 5: Media and media dependent layers;
— Part 6: Interfaces;
— Part 7: System management;
NOTE Part 2 has been withdrawn.
———————

This document was prepared with the help of CENELEC co-operation partner KNX Association, De Kleetlaan 5, B-

1831 Diegem.
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SIST EN 50090-5-2:2020
EN 50090-5-2:2020 (E)
Introduction

According to OSI, Physical Layers consist of the medium, the cable, the connectors, the transmission

technology etc. which refers to their hardware requirements. In this document however, the status of the

Physical Layer as a “communication medium” is emphasized.
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SIST EN 50090-5-2:2020
EN 50090-5-2:2020 (E)
1 Scope

This document defines the mandatory and optional requirements for the medium specific physical and

data link layer for HBES Class 1 Twisted Pair TP1.

Data link layer interface and general definitions, which are media independent, are given in

EN 50090-4-2.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

EN 50090-1, Home and Building Electronic Systems (HBES) — Part 1: Standardization structure

EN 50090-2-2, Home and Building Electronic Systems (HBES) — Part 2-2: System overview — General

technical requirements

EN 50090-3-2, Home and Building Electronic Systems (HBES) — Part 3-2: Aspects of application — User

process for HBES Class 1

EN 50090-4-2, Home and Building Electronic Systems (HBES) — Part 4-2: Media independent layers —

Transport layer, network layer and general parts of data link layer for HBES Class 1

EN 50290 (series), Communication cables

EN 61000-4-5, Electromagnetic compatibility (EMC) — Part 4-5: Testing and measurement techniques —

Surge immunity test (IEC 61000-4-5)

EN 61000-6-1, Electromagnetic compatibility (EMC) — Part 6-1: Generic standards — Immunity for

residential, commercial and light-industrial environments (IEC 61000-6-1)

EN 61000-6-2, Electromagnetic compatibility (EMC) — Part 6-2: Generic standards — Immunity for

industrial environments (IEC 61000-6-2)

HD 21.2 S2, Polyvinyl chloride insulated cables of rated voltages up to and including 450/750 V — Part 2:

Test methods (IEC 60227-2)

HD 22.2 S2, Rubber insulated cables of rated voltages up to and including 450/750 V — Part 2: Test

methods (IEC 60245-2)

IEC 60189-2, Low-frequency cables and wires with PVC insulation and PVC sheath — Part 2: Cables in

pairs, triples, quads and quintuples for inside installations

IEC 60332-1, Tests on electric cables under fire conditions — Part 1: Test on a single vertical insulated

wire or cable

IEC 60754-2, Test on gases evolved during combustion of materials from cables — Part 2: Determination

of acidity (by pH measurement) and conductivity
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EN 50090-5-2:2020 (E)
3 Terms, definitions and abbreviations
3.1 Terms and definitions

For the purposes of this document, the terms and definitions given in EN 50090-1 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1.1
HBES class 1 twisted pair type 1

physical layer specification for data and power transmission on a single twisted pair, allowing

asynchronous character-oriented data transfer in a half-duplex, bi-directional communication mode, using

a specifically balanced/symmetrical base-band signal coding with collision avoidance under SELV

conditions
3.1.2
distributed power supply

powers the bus in a distributed way by a number of the devices connected to the line (compared to a

centralized power supply)
3.1.3
logical tag extended HEE
usage of the L_Data_Extended frame dedicated to extended group addressing
3.1.4
remote powered devices
RPD

do not extract their energy for the application circuit and the bus controller from the bus but from another

independent source of energy, e.g. mains

Note 1 to entry: Owing to the reduced DC power consumption of RPD, a bus line equipped with such devices

requires less power from the installed Power Supply Unit (PSU). The connection of bus-controller and application to

the same electrical potential reduces the effort of galvanic separation in RPD.
3.1.5
TP1 backbone couplers
15 can be used to couple up to 16 zones to a full sized TP1 network
3.1.6
TP1 backbone line
main line of the inner zone is called backbone line
3.1.7
TP1 bridge
four TP1-64 physical segments can be combined to a line by using bridges
Note 1 to entry: 256 devices can then be connected to such a line.
3.1.8
TP1 line

consists of a maximum of 256 devices, either directly connected in case of TP1-256 or separated over 4

physical segments in case of TP1-64, each with 64 devices
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EN 50090-5-2:2020 (E)
3.1.9
TP1 line couplers
routers that combine lines to a zone
3.1.10
TP1 logical unit

converts the serial bit stream to octets and octets to the serial bit stream, which is a serial stream of

characters
3.1.11
TP1 medium access unit

converts information signals to analogue signals and vice versa, typically extracts DC power from the

medium
3.1.12
TP1 main line
inner line of a zone
3.1.13
TP1 physical segment
smallest entity in the TP1 topology

Note 1 to entry: To a physical segment up to 64 devices can be connected in case of TP1–64 and 256 in case of

TP1–256.
3.1.14
TP1 Polling Master
Poll_Data master
device transmitting the Poll_Data frame
3.1.15
TP1 polling slave
Poll_Data slave
device transmitting a Poll_Data character
3.1.16
TP1 router

acknowledges frames on data link layer and transmits the received frame on the other side of the router,

provided the device associated with the destination address is located on the other side

3.1.17
TP1 sub-line
outer lines of a zone
3.1.18
TP1 zone
16 TP1 lines can be connected to a zone by using 15 routers
3.2 Abbreviations
AC alternating current
ACK acknowledge
APDU application layer protocol data unit
AT address type
CSMA/CA carrier sense, multiple access with collision avoidance
CKS checksum
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SIST EN 50090-5-2:2020
EN 50090-5-2:2020 (E)
DA destination address
DC direct current
DL TP data link layer type twisted pair
DPS distributed power supply
CTRL control field
HBES Class 1 refers to simple control and command
HBES Class 2 refers to class 1 plus simple voice and stable picture transmission
HBES Class 3 refers to class 2 plus complex video transfers
IFT inter-frame-time
LC line coupler
LN length
LPDU link layer protocol data unit
LSDU link layer service data unit
LTE-HEE logical tag extended hee
MAU medium attachment unit
NACK negative acknowledge
NPCI network layer protocol control information
NRZ non-return-to-zero
OCP over-current protection
PELV protective extra low voltage
PDU protocol data unit
PSU power supply unit
RPD remote powered bus devices
RUP reverse polarity protection
SA source address
SDU service data unit
SELV safety extra low voltage
TP twisted pair
TPDU transport layer protocol data unit
UART universal asynchronous receiver transmitter
up power up
4 Requirements for HBES Class 1, Twisted Pair Type 1 (TP1-64 and TP1-256)
4.1 Physical layer requirements – Overview

The Physical Layers described in this clause are called Physical Layer type twisted pair TP1-64 and

twisted pair TP1-256. The main differences are shown in Table 1. TP1-256 is backwards compatible

towards TP1-64. If common features of TP1-64 and TP1-256 are described, only the expression TP1 is

used.
The Twisted Pair medium TP1 characteristics are:
— data and power transmission with one pair of wires;
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SIST EN 50090-5-2:2020
EN 50090-5-2:2020 (E)
— asynchronous character-oriented data transfer;
— half duplex bi-directional communication;

— a specifically balanced/symmetric base-band signal coding under SELV conditions.

All characteristics given in the following subclauses, for instance maximum number of devices or possible

cable length per physical segment are only valid for cable complying to the requirements as shown in 4.4

and for TP1 devices of which bus power consumption does not exceed 12 mA .
Table 1 — System parameters of physical layer Type TP1–64 and TP1–256
Characteristics Description TP1–64 Description TP1–256
Medium a
Shielded twisted pair
Topology Linear, star, tree or mixed
Baud rate 9 600 bps
Device supplying Normal: bus powered devices - optional: remote powered
devices
Device power consumption 3 mA to 12 mA
Power Supply Unit (PSU) DC 30 V
Number of PSUs per physical Maximum 2
segment
Number of connectable devices per Maximum 64 Maximum 256
physical segment
Number of addressable devices per b Maximum 255
Maximum 255
physical segment
Total cable length per physical Maximum 1 000 m
segment
Distance between two devices Maximum 700 m
Total number of devices in a network More than 65 000 (with More than 65 000
bridges)
Protection against shock SELV (Safety Extra Low Voltage)
Physical signal Balanced/symmetric baseband signal encoding

The shield is not mandatory, shielded cables with earth connection can improve noise immunity.

In TP1–64 a physical segment can be extended with up to 3 extra physical segments, each connected to it via a

bridge. Every physical segment can contain 63 devices.

Figure 1 shows the logical structure of the physical layer type TP1 entity. Every device includes one;

every router and bridge is equipped with two such physical layer type TP1 entities.

The physical layer type TP1 entity consists of four blocks:
— cable (medium);
— connector, connecting a device or a bridge to the transmission medium;
— a Medium Attachment Unit (MAU);
———————

Fan-in model allowing devices of which the bus power consumption is higher is under consideration.

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SIST EN 50090-5-2:2020
EN 50090-5-2:2020 (E)
— logical unit.
Figure 1 — Logical structure of physical layer type TP1

Figure 2 shows the relationship between the bits of an octet and the Universal Asynchronous Receiver

Transmitter (UART) character data bits.
Figure 2 — Octet mapped to a serial character
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SIST EN 50090-5-2:2020
EN 50090-5-2:2020 (E)
4.2 Requirements for analogue bus signals
4.2.1 General

In the underneath description, U is an internal reference voltage for the DC part of the bus voltage,

REF

used by the transmitter/receiver for evaluating the sent/received signal levels. This reference voltage is

sampled before the start bit of a byte. This U may vary with the values given in 4.2.5.

REF

The underneath specifications classify a 0 and 1 signal on the bus: the requirements for signal generation

and extraction for the transmitter and receiver respectively are defined in 4.3.2.6 and 4.3.2.7.

4.2.2 Specification of logical “1”

A logical “1” shall be regarded as the idle state of the bus, which means that the transmitter of a MAU

shall be disabled during sending a “1”. The analogue signal at the bus consists normally only of the DC-

part. There is no difference between sending a “1” and sending nothing. A decline of voltage during a “1”

may occur, if a ‘0 bit’ was preceding. The graph shall be within the shaded areas of Figure 3.

Figure 3 — “1”-Bit frame

The characteristics of a logical 1 signal shall follow the values given in Table 2.

Table 2 — Analogue and digital signal of a logical “1”
Parameter Value
Bit-time 104 µs
Voltage (DC-part) 21 to 32 V DC
Slopes (AC-part) Maximum 400 mV/ms
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SIST EN 50090-5-2:2020
EN 50090-5-2:2020 (E)
4.2.3 Specification of logical “0” (Single)

A logical “0” shall be a defined voltage drop (U ) of the analogue bus signal with a duration of t (see

a active

Figure 4). During the following equalization time the voltage may be higher than the DC-part to enable

recharging of energy consumed during the active part. The graph shall be within the shaded areas of

Figure 4.
Figure 4 — “0”-Bit frame

The characteristics of a logical “0” signal shall follow the values given in Table 3.

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SIST EN 50090-5-2:2020
EN 50090-5-2:2020 (E)
Table 3 — Analogue and digital signal of logical “0”
Parameter / Point Minimum Maximum
Bit-time 104 µs (typical)
t 35 µs (typical)
active
t (time between Ua > A and Ua > B) 25 µs 70 µs
(see also 0)
Time (Point D - E) 50 µs
Voltage (DC-part) 21 V 32 V
Voltage Ua (Point A) compared to Ref - 0,7 V - 10,5 V
Voltage Ua (Point B) compared to Ref - 0,1 V - 10,5 V
Voltage Ue (Point C - D) compared to Ref 0 V + 13 V
Voltage Uend (Point F) compared to Ref - 0,35 V + 1,8 V
4.2.4 Specification of logical “0” (overlapping)

Overlapping means, that a logical “0” is transmitted at the same time by several devices (e.g. common

ACK). Owing to the propagation delay of the bus cable (PhL-Medium) a time shift of logical zeros can

occur, if sending devices are located at a distance from the receiving devices. The MAU and the Logical

Unit shall be able to detect and interpret these signals. Figure 5 shows an example of two mixed logical

“0” that have a delay (td) of about 10 µs. Assuming that the point of measuring is at device A, the signal of

device B appears after 10 µs with a lower signal amplitude than device A, as it has been damped along

the bus cable.
Figure 5 — Delayed logical “0”
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SIST EN 50090-5-2:2020
EN 50090-5-2:2020 (E)
Figure 6 — Overlapping of two logical “0” (example)

The receiver of the MAU converts this mixed analogue signal to a digital signal. This digital signal differs

from that of a normal “0”, because the width of the receiver’s output pulse is the sum of t + td.

active

However, it is possible, that the receiver’s output delivers a gap at the end of t (See shaded area in

active

Figure 6.) This behaviour requires dedicated decoding software that is able to decode such effects.

4.2.5 Analogue requirements within a transmitted character

4.2.2 and 4.2.3 describe the voltage shape and timing when transmitting a single logical bit. When

transmitting an entire character (consists of a series of bits), the additional requirements of Table 4 shall

be met. The values Ua* and Ue* are referred to Uref at the beginning of the active part of the first bit of

the transmitted character.
Table 4 — Limits within a character
Parameter Value
Ua* Maximum - 10,5 V
Ue* Maximum 11,5 V
Uref (any bit) Maximum - 1 V / + 3 V
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EN 50090-5-2:2020 (E)
4.2.6 Simultaneous sending / collision behaviour

Although devices shall investigate the bus line before they begin sending, it is possible that two or more

devices send simultaneously. Simultaneous sending of a character occurs when two or more devices

simultaneously transmit ACK, Negative Acknowledgement (NACK) or BUSY messages.

Simultaneous transmission of a logical “0” and a logical “1” will result in a logical “0”.

Simultaneous sending of logical “0” by several devices will result in a signal that is nearly identical to that

of a single transmitting device, as signals are coded in the baseband.
This common signal shall therefore also comply with the values given in Table 2.

If a sending device detects that its own logical “1” was overwritten by another logical “0”, transmission

shall be disabled after this bit. Receiver of both devices shall however remain active.

This behaviour of the physical layer allows a CSMA/CA medium access in data link layer (see 4.8).

4.3 Medium attachment unit (MAU)
4.3.1 General

The medium attachment unit (MAU) shall split the analogue signal of the medium into the DC part and the

serial bit stream. Vice versa the serial bit stream shall be converted to the analogue bus signal.

The DC-part may be used internally to supply the device with power by using a DC/DC converter or

voltage regulator. A wrongly connected MAU shall neither damage the device nor influence the bus

communication.
4.3.2 Requirements within a physical segment
4.3.2.1 General
Within a physical segment the following principal requirements shall be met:

— in an installed system the DC voltage at every device shall be at least 21 V. Devices shall continue to

operate with a DC voltage down to 20 V. The difference between 20 V and 21 V has been laid down

as a reserve;

— the propagation delay of the serial bit stream at the MAU shall be short enough to allow bit-wise

CSMA/CA arbitration during a bit time. The total delay (MAU - Cable - MAU) shall not exceed 12 µs.

Refer also to 4.8.3;

— the Power Supply Unit [PSU(s)] connected to a physical segment shall provide the necessary

effective current required by the devices connected to the physical segment;
SELV requirements shall be met according to EN 50090-2-2.
4.3.2.2 Power up behaviour

Powering up means, that either a single bus device is installed in a ‘running’ bus segment or a PSU is

switched on in a fully equipped bus segment. The rising of the bus voltage is different. Power up

behaviour can be divided into two steps:

— during Start-up, the internal capacitors are being charged with a current limitation;

— during Operation, the capacitors are charged, voltages are constant.
Power up behaviour requires, that

— bus devices run up properly regardless the installed (allowed) topology, when the associated

segment is powered on by the PSU (slow ramp);
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EN 50090-5-2:2020 (E)

— a single bus device runs up properly if installed in an operating bus segment. Other bus devices

already installed in this segment shall not suffer a ‘reset’ owing to the installation of this additional

bus device (steep ramp);

— a possible signal disturbance, caused by the installation of a single bus device in an operating

segment shall not exceed 20 ms, in order to avoid telegram losses.
4.3.2.3 Power down behaviour

The Power down behaviour occurs when the input to the power converter of the device breaks down. This

input can either be the DC part of the bus voltage or a remote power source (see 4.3.3).

The Power Down behaviour can be divided into three steps:
— during Operation, the capacitors are charged, voltages are constant;
— during hold-up, the Capacitors are discharged;
— during Idle, the power converter draws only a leakage current.

When passing from operation to hold-up, the physical layer may generate a U signal:

save
— to allow devices to backup data before power breaks down,
— to disable further transmission of telegrams by the bus device.

For bus powered devices, this U signal shall be generated when the bus voltage drops below

save
maximal 20 V, thereby taking into account a hysteresis of at least 1 V.

The physical layer shall generate a Reset Signal U when the correct functioning of the power

reset
converter can no longer be ensure
...

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