Road vehicles -- Interchange of digital information on electrical connections between towing and towed vehicles

This document describes the data link layer (DLL) and physical layer (PHY) for the two CAN-based network interfaces specified in the 11992-series. The DLL sub-clauses are composed of: — DLL protocol entity requirements; — DLL device interface requirements; and — DLL network system requirements. Normally, the physical signalling sub-layer is implemented in the CAN protocol controller. The physical medium attachment sub-layer is normally implemented in the CAN transceiver or the System Base Chip (SBC). Optionally, it can comprise also additional protection circuitry. The media-dependent sub-layer comprises the connectors and the cabling. The physical signalling (PS) sub-clauses are composed of: — PS entity requirements; — PS device interface requirements; and — PS network system requirements. The physical medium attachment (PMA) sub-clauses are composed of: — PMA protocol entity requirements; and — PMA device interface requirements. The physical medium dependent (PMD) sub-clauses are composed of: — PMD entity requirements; — PMD device interface requirements; and — PMD network system requirements.

Véhicules routiers -- Échange d'informations numériques sur les connexions électriques entre véhicules tracteurs et véhicules tractés

General Information

Status
Published
Publication Date
01-May-2019
Current Stage
6060 - International Standard published
Start Date
02-Apr-2019
Completion Date
02-May-2019
Ref Project

RELATIONS

Buy Standard

Standard
ISO 11992-1:2019 - Road vehicles -- Interchange of digital information on electrical connections between towing and towed vehicles
English language
22 pages
sale 15% off
Preview
sale 15% off
Preview

Standards Content (sample)

INTERNATIONAL ISO
STANDARD 11992-1
Third edition
2019-05
Road vehicles — Interchange of digital
information on electrical connections
between towing and towed vehicles —
Part 1:
Physical and data-link layers
Véhicules routiers — Échange d'informations numériques sur
les connexions électriques entre véhicules tracteurs et véhicules
tractés —
Partie 1: Couche physique et couche de liaison de données
Reference number
ISO 11992-1:2019(E)
ISO 2019
---------------------- Page: 1 ----------------------
ISO 11992-1:2019(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2019

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 11992-1:2019(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 2

4 Abbreviated terms .............................................................................................................................................................................................. 4

5 Data link layer (DLL) ........................................................................................................................................................................................ 4

5.1 General ........................................................................................................................................................................................................... 4

5.2 DLL protocol entity requirements ......... ................................................................................................................................. 4

5.3 DLL device interface requirements ....................................................................................................................................... 4

6 Physical layer (PHY) .......................................................................................................................................................................................... 5

6.1 General ........................................................................................................................................................................................................... 5

6.2 Physical signalling (PS) requirements ................................................................................................................................ 5

6.2.1 General...................................................................................................................................................................................... 5

6.2.2 PS entity requirements ............................................................................................................................................... 5

6.2.3 PS device interface requirements...................................................................................................................... 5

6.3 Physical medium attachment (PMA) requirements ............................................................................................... 6

6.3.1 PMA entity requirements ......................................................................................................................................... 6

6.3.2 PMA device interface requirements .............................................................................................................13

6.4 Physical media dependent (PMD) sub-layer requirements ..........................................................................14

6.4.1 PMD entity requirements ......................................................................................................................................14

6.4.2 PMD device interface requirements .............................................................................................................14

6.5 Network wiring harness system requirements .......................................................................................................16

Annex A (informative) Implementation examples of the bus failure management .........................................20

Bibliography .............................................................................................................................................................................................................................22

© ISO 2019 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 11992-1:2019(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.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).

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

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso

.org/iso/foreword .html.

This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 31,

Data communication.

This third edition cancels and replaces the second edition (ISO 11992-1:2003) which has been

technically revised.
The main changes compared to the previous edition are as follows:
— wording improvements and clarifications;
— introduction of requirement statements; and

— addition of informative Annex A, Implementation examples of the bus failure management.

A list of all parts in the ISO 11992 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO 2019 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 11992-1:2019(E)
Introduction

The ISO 11992 series specifies the interchange of digital information between road vehicles with a

maximum authorised total mass greater than 3 500 kg. The series also specifies digital information

interchange for towed vehicles, including communication between towed vehicles in terms of

parameters and requirements of the lower OSI layers (physical and data link layer) of the electrical

connection used to connect the electrical and electronic systems.

This document specifies the data link and physical layer requirements of the CAN communication bus

between towing and towed vehicles.

This document has been structured according to the Open Systems Interconnection (OSI) Basic

Reference Model, in accordance with ISO/IEC 7498-1 and ISO/IEC 10731, which structures

communication systems into seven layers. When mapped on this model, the application protocol and

data link layer framework requirements specified/referenced in a ISO 11992 series standard are

structured according to Figure 1.
Figure 1 illustrates the following communication frameworks:
— normal vehicle communication framework;
— vehicle diagnostic communication framework;
— vehicle-specific use case framework; and
— vehicle lower-layers framework.

The normal vehicle communication framework is composed of ISO 11992-2 and ISO 11992-3.

[3] [12]

The vehicle diagnostic communication framework is composed of ISO 14229-1 , ISO 14229-2 ,

[13] [3]
ISO 14229-3 and ISO 11992-4 .

The vehicle-specific use case framework is composed of ISO 11992-4, ISO 22901-1 or vehicle

manufacturer-specific diagnostic data definition.
[14] [6]

The vehicle lower-layers framework is composed of ISO 15765-2 , ISO 11898-1, 1, ISO 7638-1 and

[10]
ISO 12098 .
© ISO 2019 – All rights reserved v
---------------------- Page: 5 ----------------------
ISO 11992-1:2019(E)

Figure 1 — Towing and towed vehicles framework documents reference according to the OSI

model
Figure 2 shows the implementation example of the lower-layers block diagram.
vi © ISO 2019 – All rights reserved
---------------------- Page: 6 ----------------------
ISO 11992-1:2019(E)
Figure 2 — Implementation example of lower-layers block diagram

The above requirements structure has been chosen to provide the following developers with relevant

requirements:
— transceiver developers;
— device (e.g., electronic control unit) developers; and
— towing and towed vehicle network developers.

All requirements are numbered and headlined uniquely, so that each implementer can reference them.

© ISO 2019 – All rights reserved vii
---------------------- Page: 7 ----------------------
INTERNATIONAL STANDARD ISO 11992-1:2019(E)
Road vehicles — Interchange of digital information
on electrical connections between towing and towed
vehicles —
Part 1:
Physical and data-link layers
1 Scope

This document describes the data link layer (DLL) and physical layer (PHY) for the two CAN-based

network interfaces specified in the 11992-series.
The DLL sub-clauses are composed of:
— DLL protocol entity requirements;
— DLL device interface requirements; and
— DLL network system requirements.

Normally, the physical signalling sub-layer is implemented in the CAN protocol controller. The physical

medium attachment sub-layer is normally implemented in the CAN transceiver or the System Base Chip

(SBC). Optionally, it can comprise also additional protection circuitry. The media-dependent sub-layer

comprises the connectors and the cabling.
The physical signalling (PS) sub-clauses are composed of:
— PS entity requirements;
— PS device interface requirements; and
— PS network system requirements.
The physical medium attachment (PMA) sub-clauses are composed of:
— PMA protocol entity requirements; and
— PMA device interface requirements.
The physical medium dependent (PMD) sub-clauses are composed of:
— PMD entity requirements;
— PMD device interface requirements; and
— PMD network system requirements.
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.

ISO 4141-1, Road vehicles — Multi-core connecting cables — Part 1: Test methods and requirements for

basic performance sheathed cables
© ISO 2019 – All rights reserved 1
---------------------- Page: 8 ----------------------
ISO 11992-1:2019(E)

ISO 11898-1, Road vehicles — Controller area network (CAN) — Part 1: Data link layer and physical

signalling
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

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

— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
3.1
1-wire operation

communication on either CAN_L or CAN_H with reference to ground and V potential during fault-

tolerant operation mode
3.2
2-wire operation

communication on CAN_L and CAN_H, with reference to ground and V potential, in nominal (non fault-

tolerant) operation mode
3.3
bus
communication link between two communication entities
3.4
CAN_H
CAN_L
particular cable and/or contact of the communication connection
3.5
differential transmission

transmission of digital information carried by voltage between the two conductors of the electrical

connections
3.6
maximum authorised total mass

vehicle mass determined as a maximum by the administrative authority for operating conditions laid

down by that authority

Note 1 to entry: In some jurisdictions this will be known as the Gross Vehicle Weight Rating or the Gross

Combination Weight Rating.

[SOURCE: ISO 1176:1990, 4.8, modified — NOTES 1 and 2 replaced by a new Note 1 to entry]

3.7
data link layer protocol entity
DLL protocol entity

functional part of the electronic component implementing the DLL protocol as standardised in

ISO 11898-1
3.8
data link layer device interface
DLL device interface

electronic device interface compliant with ISO 11898-1 optionally with functional restrictions

EXAMPLE No transmission of remote frames or transmission of extended frame formatted messages only.

2 © ISO 2019 – All rights reserved
---------------------- Page: 9 ----------------------
ISO 11992-1:2019(E)
3.9
data link layer network system
DLL network system

logical DLL system comprising two additional interoperable nodes compliant with ISO 11898-1

3.10
physical signalling entity
PS entity

functional part of the electronic component implementing the DLL protocol as standardised in

ISO 11898-1
3.11
physical signalling device interface
PS device interface

electronic interface compliant with ISO 11898-1 and detailed bit-timing configuration including

configured re-synchronisation capability
3.12
physical signalling network system
PS network system

network with devices with an interoperable bit-timing and bit synchronisation compliant with

ISO 11898-1
3.13
physical medium attachment entity
PMA entity

electronic component (transceiver) or part of an electronic component (system base chip)

3.14
physical medium attachment device interface
PMA device interface

electronic device interface comprising a PMA entity and optionally additional circuitry

3.15
physical medium attachment network system
PMA network system

network system comprising two devices with physical media attachment interfaces compliant to this

document
3.16
physical medium dependent entities
PMD entities
connectors, cabling, and other electro-mechanical network components
3.17
physical medium dependent device interface
PMD device interface
connectors, cabling, and other electro-mechanical components
3.18
physical medium dependent network system
PMD network system
electro-mechanical interface of a single device
3.19
towed vehicle
unpowered vehicle that is towed by a towing vehicle or another unpowered vehicle
[SOURCE: ISO 3833:1977, 3.2, modified — definition editorially revised]
© ISO 2019 – All rights reserved 3
---------------------- Page: 10 ----------------------
ISO 11992-1:2019(E)
3.20
towing vehicle
motor vehicle or unpowered vehicle, which tows a succeeding unpowered vehicle
4 Abbreviated terms
AC alternating current
CAN controller area network
CEFF classical extended frame format
DC direct current
DLL data link layer
ECU electronic control unit
PHY physical layer
PMA physical medium attachment
PMD physical medium dependent
PS physical signalling
5 Data link layer (DLL)
5.1 General

The data link layer provides the functional and procedural means to transfer data between network

devices and provides the means to detect and possibly correct errors that can occur in the physical

layer. The DLL is concerned with local delivery of frames (PDUs) between devices on the CAN network.

The DLL endeavours to arbitrate between parties contending for access to a medium, without concern

for their ultimate destination. When devices attempt to use a medium simultaneously, frame collisions

occur. The data-link protocol specifies how devices detect and recover from such collisions and may

provide mechanisms to reduce or prevent them.
5.2 DLL protocol entity requirements

The DLL protocol entity transfers data between network nodes on the CAN network. The following

requirements are applicable.
REQ 2.1 DLL — ISO 11898-1
The DLL protocol entity shall comply with ISO 11898-1.
5.3 DLL device interface requirements
REQ 2.2 DLL — Allowed data frame format

The DLL device interface shall transmit only data frames in CEFF (Classical Extended Frame Format).

REQ 2.3 DLL — Remote frames

The DLL device interface shall not request remotely data frames by means of remote frames.

4 © ISO 2019 – All rights reserved
---------------------- Page: 11 ----------------------
ISO 11992-1:2019(E)
6 Physical layer (PHY)
6.1 General
The PHY is divided in three sub-layers:
— physical signalling (PS),
— physical medium attachment (PMA), and
— physical medium dependent (PMD) sub-layers.
6.2 Physical signalling (PS) requirements
6.2.1 General

The physical signalling sub-layer, as specified in ISO 11898-1, determines the transmission speed and

the recent re-synchronisation capability.
6.2.2 PS entity requirements

The physical signalling entity is normally part of the CAN controller implementation.

REQ 1.1 PHY — PS entity requirements — ISO 11898-1 conformance
The PS entity shall comply with ISO 11898-1.
REQ 1.2 PHY — PS entity requirements — Fault confinement

The fault confinement entity used for the data link layer shall be in accordance with ISO 11898-1.

6.2.3 PS device interface requirements

The bit-timing settings determine the transmission speed and the re-synchronisation capability. The

programming of the bit time depends on the internal signal delay time and the capacitive load.

REQ 1.3 PHY — PS device interface requirements — Bit-rate

The PS device shall be configured that it transmits frames at a bit-rate of 125 kbit/s.

REQ 1.4 PHY — PS device interface requirements — Oscillator frequency

The oscillator frequency from which the data rate is derived shall have a maximum relative tolerance

of ±0,01 %.
REQ 1.5 PHY — PS device interface requirements — Bit timing settings

To ensure proper operation under worst case conditions, the parameters specified in Table 1 shall apply

and following requirements shall be fulfilled.

— Only signal edges from recessive-to-dominant-shall be used for synchronisation.

— Single sampling shall be used.
© ISO 2019 – All rights reserved 5
---------------------- Page: 12 ----------------------
ISO 11992-1:2019(E)
Table 1 — Bit timing parameters
Value
Parameter Notation Unit
Min. Nominal Max.
Bit time without synchronisation (logical) t µs 7,999 2 8,0 8,000 8
Internal signal delay time t µs — — 0,4
del
Synchronisation jump width t ns — — 500
sjw
Sample point t µs 6 + t — 7
sjw

Period of time between transmit logic input signal and receive logic output signal at state transition, bus length = 0 m.

See ISO 11898-1.
6.3 Physical medium attachment (PMA) requirements
6.3.1 PMA entity requirements
REQ 1.6 PHY — PMA entity requirements — PMD interface

The PMA entity shall provide the differential voltage V as specified in Equation (1).

diff
REQ 1.7 PHY — PMA entity requirements — Dominant state

In the logical “dominant” state, the voltage levels of CAN_H and CAN_L shall be as specified in Equation (2).

REQ 1.8 PHY — PMA entity requirements — Recessive state

In the logical "recessive" state, the voltage levels of CAN_H and CAN_L shall be as specified in Equation (3).

Definition of Equation (1)
VV=−V (1)
diff CAN_LCAN_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
Definition of Equation (2)
VV=×
CAN_Hs
(2)
VV=×
CAN_Ls
where V is the supply voltage of the device connected to the bus.
Definition of Equation (3)
VV=×
CAN_Hs
(3)
VV=×
CAN_Ls
Figure 3 shows the dominant and recessive state of CAN_H and CAN_L.
6 © ISO 2019 – All rights reserved
---------------------- Page: 13 ----------------------
ISO 11992-1:2019(E)
Key
0 dominant: Logic "0"
1 recessive: Logic "1"
Figure 3 — Dominant and recessive state of CAN_H and CAN_L
REQ 1.8 PHY — PMA entity requirements — DC parameters

The DC parameter of a PMA entity shall be within the ranges specified in Table 2 and Table 3, as appro-

priate. The parameters are valid for 2-wire operation, and for non-affected parts of the interface in the

case of 1-wire operation.

Table 2 specifies the DC parameters for the recessive state with the two connectors mated.

Table 2 — DC parameters for the recessive state
Value
Parameter Notation Unit
min. nominal max.

Voltage level if TXD and RXD (see Figure 2) are in high-im- V 0,32 × V 0,33 × V 0,35 × V

CAN_H s s s
pedance state
V V 0,65 × V 0,67 × V 0,68 × V
CAN_L s s s
Differential voltage V — 0,33 × V —
diff s
Threshold of differential voltage for receiving a recessive bit V V 0 — 0,65
diff-th
Table 3 specifies the DC parameters for the dominant state.
Table 3 — DC parameters for the dominant state
Value
Parameter Notation Unit
min. nominal max.
V 0,64 × V 0,67 × V 0,70 × V
CAN_H s s s
Voltage level
V V 0,30 × V 0,33 × V 0,36 × V
CAN_L s s s
Differential voltage V — −0,33 × V —
diff s
Threshold of differential voltage for receiving a dominant bit V V −0,65 — 0
diff-th
CAN_H
Current for the entire range of V mA — 13,3 (6,6) —
CAN_L
Two interfaces coupled with the connector, only one transmits.

Two interfaces coupled. The values within brackets apply to nominal 12-V voltage systems; those without brackets

apply to nominal 24-V voltage systems.
© ISO 2019 – All rights reserved 7
---------------------- Page: 14 ----------------------
ISO 11992-1:2019(E)
REQ 1.9 PHY — PMA entity requirements — Time constant t
The time constant t shall be in accordance to Equation (4). See also REQ 1.21.
Definition of Equation (4)
XV=+06, 3×−VV (4)
CAN_L1 CAN_L2 CAN_L1

Figure 4 shows an example of time constant t , which is the delay of voltage change between V and

F s
V or V in the case of any changes of V .
CAN_H CAN_L s
Figure 4 — Example of time constant t
[4] [5]

Transient errors (e.g. according ISO 7637-1 and ISO 7637-2 ) are handled by the DLL entity (see

ISO 11898-1).
REQ 1.10 PHY — PMA entity requirements — CAN bus-off state

When a node is set into the bus-off state it shall be immediately reset to resume communication. Failure

handling depends on the repetition times, t , of the initialisation messages. Failures in the data trans-

mission which are only present for less than 5 t shall not be indicated to the data link layer entity. In

such case, the PMA interface shall remain in the 2-wire operation mode.
8 © ISO 2019 – All rights reserved
---------------------- Page: 15 ----------------------
ISO 11992-1:2019(E)

Some bus faults as shown in Figure 5 can impact the proper operation of the PMA entity.

REQ 1.11 PHY — PMA entity requirements — Electrical circuit

An electrical circuit shall be provided to avoid a total breakdown of the data transmission during bus

failures. This circuit shall have the capability to transition from 2-wire-to 1-wire operation mode using

only one of the two wires CAN_H or CAN_L.

This allows data transmission to be maintained in the case of an interruption of CAN_H or CAN_L, or a

short circuit of one cable to ground or to supply voltage, or a short circuit between CAN_H and CAN_L

(see bus fault cases 1, 2, 3, 4, 5, 6 and 7 in Figure 5). Data transmission is no longer possible if both

cables are affected by a short circuit (except a short circuit between CAN_H and CAN_L) or interruption

(bus fault case 8). Implementation examples are given in Annex A.
Key
1 bus fault case 1 — CAN_H broken wire
2 bus fault case 2 — CAN_L broken wire
3 bus fault case 3 — CAN_L short to V
4 bus fault case 4 — CAN_L short to ground
5 bus fault case 5 — CAN_H short to ground
6 bus fault case 6 — CAN_H short to V
7 bus fault case 7 — CAN_H and CAN_L shorted
8 bus fault case 8 — CAN_H and CAN_L broken wire
9 device towing vehicle
10 ground
11 device towed vehicle
Figure 5 — Bus fault cases
REQ 1.12 PHY — PMA entity requirements — Bus fault detection

If correct data transmission is not possible for longer than 5 t (data neither correctly received nor trans-

mitted), then the fault handling logic shall indicate this and perform the bus fault handling procedure

described in REQ 2.15 to REQ 2.16.

NOTE 1 The bus fault detection and handling is realised either by hardware or software.

REQ 1.13 PHY — PMA entity requirements — 1-wire bus fault operation mode 1 handling

(cases 1 to 6)

In the CAN_L-operation mode the dominant driver of CAN_H shall be switched off and the voltage at

the receive-comparator for CAN_H shall be replaced by a reference voltage. This mode shall be used to

cover bus fault case 1, bus fault case 5, and bus fault case 6 of Figure 5.
© ISO 2019 – All rights reserved 9
---------------------- Page: 16 ----------------------
ISO 11992-1:2019(E)

REQ 1.14 PHY — PMA entity requirements — 1-wire bus fault operation mode 2 handling

(case 1 to case 6)

In the CAN_H operation mode the dominant driver of CAN_L shall be switched off, the recessive

source of CAN_L switched to a high impedance state, and the voltage at the receive-comparator for

CAN_L shall be replaced by a reference voltage. This mode shall be used to cover bus fault cases 2, 3,

and 4 of Figure 5.
REQ 1.15 PHY — PMA entity requirements — 1-wire bus fault handling case 7

Bus fault case 7 of Figure 5 shall be covered by either CAN_L-operation mode or CAN_H-operation mode.

NOTE 2 The bus fault detection and handling can be a procedure realised either by hardware or software.

Depending on the bus fault case, one of the two operation modes allow successful data transmissions.

This mode is called the "correct 1-wire operation mode". It could be necessary to try both 1-wire

operation modes before identifying the correct 1-wire operation mode.

The fault handling procedure in the towing vehicle starts when data transmission is not possible for 5 t .

REQ 1.16 PHY — PMA entity requirements — Switch to 1-wire operation mode

The fault handling procedure shall then switch to a 1-wire operation mode and try to work in this mode

for 10 t . If during this time no data transmission is successful, the interface shall switch to the other

1-wire operation mode and try to operate in this mode for 10 t .

If during this time data transmission is still not successful, the interface shall switch to the 2-wire op-

eration mode and start the fault detection and handling procedure again with a 5 t observation period.

The fault handling procedure in the towed vehicles starts when data transmission is not possible for 5 t .

REQ 1.17 PHY — PMA entity requirements — Switch to correct 1-wire operation mode

The fault handling shall perform a procedure that guarantees that the towed vehicle switches to the

correct 1-wire operation mode within 6 t , after the interface of the towing vehicle switched to the cor-

rect 1-wire operation mode and that it then remains in that mode.

If no data transmission is successful for 20 t , the interface shall switch to the 2-wire operation mode

and start that fault detection and handling procedure again with a 6 t observation period.

REQ 1.18 PHY — PMA entity requirements — Resume successful data transmission

As soon as data transmission is successful again, the current operation mode shall be continued, and

the fault detection and handling sequence shall be restarted with a 5 t observation period of the line

or lines used.

An example of the timing diagram for bus failure, case 6 = CAN_H short to V , is shown in Figure 6.

10 © ISO 2019 – All rights reserved
---------------------- Page: 17 ----------------------
ISO 11992-1:2019(
...

Questions, Comments and Discussion

Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.