ISO 11992-1:1998
(Main)Road vehicles — Electrical connections between towing and towed vehicles — Interchange of digital information — Part 1: Physical layer and data link layer
Road vehicles — Electrical connections between towing and towed vehicles — Interchange of digital information — Part 1: Physical layer and data link layer
Véhicules routiers — Connexions électriques entre véhicules tracteurs et véhicules tractés — Échange de données numériques — Partie 1: Couche physique et couche liaison de données
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 11992-1
First edition
1998-04-01
Road vehicles — Electrical connections
between towing and towed vehicles —
Interchange of digital information —
Part 1:
Physical layer and data link layer
Véhicules routiers — Connexions électriques entre véhicules tracteurs et
véhicules tractés — Échange de données numériques —
Partie 1: Couche physique et couche liaison de données
A
Reference number
ISO 11992-1:1998(E)
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ISO 11992-1:1998(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO
member bodies). The work of preparing International Standards is normally carried out through ISO technical
committees. Each member body interested in a subject for which a technical committee has been established has
the right to be represented on that committee. International organizations, governmental and non-governmental, in
liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.
International Standard ISO 11992-1 was prepared by Technical Committee ISO/TC 22, Road vehicles,
Subcommittee SC 3, Electrical and electronic equipment.
ISO 11992 consists of the following parts, under the general title Road vehicles — Electrical connections between
towing and towed vehicles — Interchange of digital information:
— Part 1: Physical layer and data link layer
— Part 2: Application layer for braking equipment
— Part 3: Application layer for non-braking equipment
© ISO 1998
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic
or mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 • CH-1211 Genève 20 • Switzerland
Internet central@iso.ch
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Printed in Switzerland
ii
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INTERNATIONAL STANDARD © ISO ISO 11992-1:1998(E)
Road vehicles — Electrical connections between towing and towed
vehicles — Interchange of digital information —
Part 1:
Physical layer and data link layer
1 Scope
This part of ISO 11992 specifies the interchange of digital information between road vehicles with a maximum
authorised total mass greater than 3 500 kg, and towed vehicles, including communication between towed vehicles
in terms of parameters and requirements of the physical and data link layer of the electrical connection used to
connect the electrical and electronic systems.
It also includes conformance tests of the physical layer.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this part of
ISO 11992. At the time of publication, the editions indicated were valid. All standards are subject to revision, and
parties to agreements based on this part of ISO 11992 are encouraged to investigate the possibility of applying the
most recent editions of the standards indicated below. Members of IEC and ISO maintain registers of currently valid
International Standards.
ISO 1176:1990, Road vehicles — Masses — Vocabulary and codes.
ISO 7637-1:1990, Road vehicles — Electrical disturbance by conduction and coupling — Part 1: Passenger cars
and light commercial vehicles with nominal 12 V supply voltage — Electrical transient conduction along supply lines
only.
ISO 7637-2:1990, Road vehicles — Electrical disturbance by conduction and coupling — Part 2: Commercial
vehicles with nominal 24 V supply voltage — Electrical transient conduction along supply lines only.
ISO 8092-2:1996, Road vehicles — Connections for on-board electrical wiring harnesses — Part 2: Definitions, test
methods and general performance requirements.
ISO 11898:1993, Road vehicles — Interchange of digital information — Controller area network (CAN) for high
speed communication, and its Amendment 1:1995.
ISO 11992-2:1998, Road vehicles — Electrical connections between towing and towed vehicles — Interchange of
digital information — Part 2: Application layer for braking equipment.
ISO 11992-3:1998, Road vehicles — Electrical connections between towing and towed vehicles — Interchange of
digital information — Part 3: Application layer for non-braking equipment.
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© ISO
ISO 11992-1:1998(E)
3 Definitions
For the purposes of this part of ISO 11992, the following definitions apply.
3.1 maximum authorised total mass
vehicle mass determined as a maximum by the administrative authority for operating conditions laid down by that
authority [ISO 1176:1990]
3.2 point-to-point connection
electrical connection between two electronic nodes only
3.3 bus
one or more conductors used for transmitting signals
3.4 line conductor
conductive part of cables used for transmitting signals
3.5 CAN_H, CAN_L
particular cable and/or contact of the communication connection
3.6 differential transmission
transmission of digital information carried by voltage between the two conductors of the electrical connections (two-
wire operation)
4 General specification
The data link layer and the fault confinement entity used for this data link shall be in accordance with ISO 11898
[Controller Area Network (CAN) for high speed communication].
5 Physical layer
5.1 General requirements
The physical layer shall be a point-to-point connection, in order to ensure satisfactory operation of both the coupled
and decoupled trailer.
Stable electrical signals with high signal-to-noise ratio are required even at extreme external operating conditions
(salt, oil, moisture, etc.).
The contact resistance and leakage currents shall not become the weak points of the braking equipment during the
lifetime of vehicles.
For safety reasons the data transmission shall be monitored, and in the case of a failure, at least one emergency
operation shall be provided.
The transmission shall be bi-directional and differential.
The nominal supply voltages of the physical layer circuits may be either 12 V or 24 V.
5.2 Physical media
5.2.1 General
The bus consists of two unscreened twisted cables, CAN_H and CAN_L, for the transmission of the differential
signals. These cables may be part of a multi-core cable. For this physical layer the characteristic impedance has no
significant influence, and is therefore left unspecified.
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ISO 11992-1:1998(E)
The total length of cable is split into at least three parts, as shown in figure 1. If more connectors are used on each
vehicle (ECU connectors, etc.) the total capacitance shall be less than C for each length, as specified in table 1.
busx
Figure 1 — Cable lengths
5.2.2 Parameters related to the cables CAN_H and CAN_L
The parameters shall be in accordance with table 1.
5.3 Contacts
5.3.1 General
The interface provides two contacts for the data transmission, CAN_H and CAN_L.
5.3.2 Parameters related to the contacts CAN_H and CAN_L
The parameters shall be in accordance with table 2.
5.4 Physical medium attachment
5.4.1 Electrical equivalent circuit diagram
Figure 2 shows the electrical equivalent circuit diagram of one unit of the data link.
CAN_H and CAN_L shall be connected to the resistances and voltage sources as specified. The data link shall fulfil
the limiting values specified in 5.4.2.
5.4.2 "Dominant" and "recessive" status, electrical parameters
5.4.2.1 Transmission levels
CAN_H and CAN_L shall be operated with the voltage levels given in figure 3.
The logic state of the bus may be "dominant" or "recessive", as specified in figure 3.
The logic "recessive" state is specified by the following voltage levels of CAN_H and CAN_L:
V = 1/3 V
CAN_H s
V = 2/3 V
CAN_L s
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ISO 11992-1:1998(E)
Table 1 — Cable parameters
Value
Parameter Notation Unit
nominal max. min.
1)
Overall cable length l m— 40 —
Cable length in towing vehicle l m— 15
1
Differential capacitance between CAN_H and CAN_L in towing C pF 750 — —
d1
vehicle
Input capacitance between CAN_H and ground, CAN_L and ground C pF 750 — —
i1
in towing vehicle
2)
Bus capacitance in towing vehicle C nF — 2,4 —
bus1
Resistance of CAN_H and CAN_L in towing vehicle R mΩ — 600 —
l1
Insulation resistance of each CAN_H and CAN_L to ground and V R —— 15
MΩ
bat i11
3)
in towing vehicle
3)
Insulation resistance between CAN_H and CAN_L in towing vehicle R MΩ —— 15
i21
Coiled cable length l m— 7 —
2
Differential capacitance between CAN_H and CAN_L in coiled cable C pF 560 — —
d2
Input capacitance between CAN_H and ground, CAN_L and ground C pF 700 — —
i2
in coiled cable
2)
Bus capacitance in coiled cable C nF — 1,9 —
bus2
Resistance of each CAN_H and CAN_L in coiled cable R — 300 —
mΩ
l2
Insulation resistance of each CAN_H and CAN_L to ground and V R —— 30
MΩ
bat i12
3)
in coiled cable
3)
Insulation resistance between CAN_H and CAN_L in coiled cable R MΩ —— 30
i22
Cable length in towed vehicle l m— 18 —
3
Differential capacitance between CAN_H and CAN_L in towed C pF 900 — —
d3
vehicle
Input capacitance between CAN_H and ground, CAN_L and ground C pF 900 — —
i3
in towed vehicle
2)
Bus capacitance in towed vehicle C nF — 2,9 —
bus3
Resistance of each CAN_H and CAN_L in towed vehicle R mΩ — 700 —
l3
Insulation resistance of each CAN_H and CAN_L to ground and V R MΩ —— 12
bat i13
3)
in towed vehicle
3)
Insulation resistance between CAN_H and CAN_L in towed vehicle R —— 12
MΩ
i23
1) l = l + l + l
1 2 3
2) The capacitive load for the driving circuit resulting from the cable is C = C + 2 C , where x = 1, 2, 3; including the
busx ix dx
connector capacitance, C .
con
3) Test method similar to ISO 8092-2.
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© ISO
ISO 11992-1:1998(E)
Table 2 — Contact parameters
Value
Parameter Notation Unit
nominal max. min.
Contact resistance R —10 —
mΩ
con
2)
Insulation resistance between CAN_H and CAN_L R MΩ —— 50
i1
Differential capacitance between CAN_H and CAN_L C pF 5 — —
cd
2)
Insulation resistance between CAN_H/CAN_L and ground R M —— 50
Ω
i2
Input capacitance between CAN_H/CAN_L and ground C pF 5 — —
ci
1)
Capacitive load of the connector C pF — 20 —
con
1) The capacitive load for the driving circuit resulting from the connector is: C = C + 2 C .
con ci cd
2) According to ISO 8092-2.
NOTE — V = Voltage source of CAN_H for recessive state, value (see 5.4.2.1).
CAN_H0
V = Voltage source of CAN_L for recessive state, value (see 5.4.2.1).
CAN_L0
Figure 2 — Electrical equivalent circuit diagram of one data link unit
The logic "dominant" state is specified by the following voltage levels of CAN_H and CAN_L:
V = 2/3 V
CAN_H s
V = 1/3 V
CAN_L s
where V is the supply voltage of the data link units connected to the bus.
s
The differential voltage V is
diff
V = V – V
diff CAN_L CAN_H
This results in a value of
V = 1/3 V at "recessive" state, and
diff s
V = –1/3 V at "dominant" state.
diff s
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© ISO
ISO 11992-1:1998(E)
Figure 3 — Specification of "dominant" and "recessive" state of CAN_H and CAN_L
5.4.2.2 Ratings
The voltage levels of V , V and V shall be within the voltage ranges specified in tables 3 and 4 as
s CAN_H CAN_L
appropriate and as in table 5.
The interface operating voltage V is the on-board supply voltage for the commercial vehicle and the trailer interface
s
as shown in figure 4. If internal protection circuits (such as filters) are used, V and V shall fulfil the
CAN_H CAN_L
specified requirements of tables 6 and 7. The time constant t shown in figure 5 specifies the delay of voltage
F
change between V and V or V in the case of any changes of V . Electrical interference along supply
s CAN_H CAN_L s
lines, defined in ISO 7637-1 and ISO 7637-2, may interrupt the communication for less than 10 ms. No failure
reaction shall occur during this time.
Table 3 — Voltage ranges for 24 V nominal voltage systems
Voltage
Parameter Notation Unit
min. nominal max.
Interface operating voltage V V16 — 32
s
V
Voltage at bus connection CAN_H V0 — 32
V
CAN_L
Interface supply current (nominal operation) I mA — — 60
s
Table 4 — Voltage ranges for 12 V nominal voltage systems
Voltage
Parameter Notation Unit
min. nominal max.
Interface operating voltage V V9 — 16
s
V
Voltage at bus connection CAN_H V0 — 16
V
CAN_L
Interface supply current (nominal operation) I mA — — 30
s
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© ISO
ISO 11992-1:1998(E)
Table 5 — Ground offset ranges
Voltage
Parameter Notation Unit
min. max.
Ground offset between the two interfaces during two-wire V V – V /8 V /8
os s s
1)
operation
Ground offset between the two interfaces during one-wire V V – V /16 V /16
os s s
1)
operation
1) The ground offset V is related to the supply voltage of the interface of the towing vehicle.
os
Figure 4 — Specification of V
s
5.4.2.3 d.c. parameters
The d.c. parameters of an interface shall be within the ranges specified in tables 6 and 7 as appropriate.
The parameters are valid for two-wire operation, and for non-affected parts of the interface in the case of one-wire
operation.
Table 6 — d.c. parameters at "recessive" state
Value
Parameter Notation Unit
min. nominal max.
V 0,32V 0,33V 0,35V
Voltage level (data link disconnected) CAN_H s s s
V 0,65V 0,67V 0,68V
CAN_L s s s
Differential voltage V V — 0,33 V —
diff s
Threshold of differential voltage for receiving a recessive bit V 0 — 0,65
diff-th
Input resistance R Ω 570 600 630
1
1)
I
Current through connector CAN_H mA — 0 —
I
CAN_L
1) With the two connectors mated.
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© ISO
ISO 11992-1:1998(E)
Table 7 — d.c. parameters at "dominant" state
Parameter Notation Unit Value
min. nominal max.
1)
V 0,64 V 0,67 V 0,70 V
Voltage level CAN_H s s s
V 0,30 V 0,33 V 0,36 V
CAN_L V s s s
Differential voltage V —– 0,33 V —
diff s
Threshold of differential voltage for receiving a dominant bit V – 0,65 — 0
diff-th
2)
I 13,3
Current through connector for the whole range of V CAN_H mA — —
s
I (6,6)
CAN_L
3)
Serial resistance R Ω 285 300 315
2
1) Two interfaces coupled with the connector, only one transmits.
2) Two interfaces coupled. The value within brackets applies to 12 V nominal voltage systems; those without brackets
apply to 24 V nominal voltage systems.
3) Including the serial resistance of the switch (compare with figure 2).
5.4.2.4 a.c. parameters
The requirements of the a.c. parameters shall be within the ranges specified in table 8.
5.4.3 Bus failure management
Transient errors (e.g. according to ISO 7637) are automatically handled by the CAN protocol as specified in
ISO 11898.
When a node is set to the bus-off state due to a more permanent failure, it shall immediately be reset to resume
communication.
Failure handling depends on the shortest nominal transmission repetition time t for all messages transmitted by the
r
interface (as in ISO 11992-2 or ISO 11992-3). Failures in the data transmission that are only present for less than
5t shall not be indicated. In this case the interface shall remain in the two-wire-operation mode.
r
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© ISO
ISO 11992-1:1998(E)
Table 8 — a.c. parameters
Value
Parameter Notation Unit
min. nominal max.
Bit time without synchronisation (logical) t μs 7,999 2 8,0 8,000 8
1)
Internal signal delay time t μs — — 0,4
del
2)
Sample point t μs 6 + t —7
sjw
3)
Input capacitance of one interface C — 400 —
i
4)
Differential input capacitance C pF — 100 —
d
5)
Bus input capacitance C — 600 800
bus
6)
Time constant of supply filter t ms — — 5
F
1) Period of time between transmit logic input signal a
...
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