Road vehicles -- Controller area network (CAN)

ISO 11898-5:2007 specifies the CAN physical layer for transmission rates up to 1 Mbit/s for use within road vehicles. It describes the medium access unit functions as well as some medium dependent interface features according to ISO 8802-2. ISO 11898-5:2007 represents an extension of ISO 11898-2, dealing with new functionality for systems requiring low-power consumption features while there is no active bus communication. Physical layer implementations according to ISO 11898-5:2007 are compliant with all parameters of ISO 11898‑2, but are defined differently within ISO 11898-5:2007. Implementations according to ISO 11898-5:2007 and ISO 11898-2 are interoperable and can be used at the same time within one network.

Véhicules routiers -- Gestionnaire de réseau de communication (CAN)

General Information

Status
Withdrawn
Publication Date
11-Jun-2007
Withdrawal Date
11-Jun-2007
Current Stage
6060 - International Standard published
Start Date
15-May-2007
Completion Date
12-Jun-2007
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INTERNATIONAL ISO
STANDARD 11898-5
First edition
2007-06-15
Road vehicles — Controller area network
(CAN) —
Part 5:
High-speed medium access unit
with low-power mode
Véhicules routiers — Gestionnaire de réseau de communication
(CAN) —
Partie 5: Unité d'accès au médium haute vitesse avec mode
de puissance réduite
Reference number
ISO 11898-5:2007(E)
ISO 2007
---------------------- Page: 1 ----------------------
ISO 11898-5:2007(E)
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© ISO 2007

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ii © ISO 2007 – All rights reserved
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ISO 11898-5:2007(E)
Contents Page

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

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

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

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

3 Terms and definitions........................................................................................................................... 1

4 Symbols and abbreviated terms ......................................................................................................... 2

5 Functional description of medium access unit (MAU) with low-power mode................................ 2

5.1 General................................................................................................................................................... 2

5.2 Physical medium attachment sub layer specification ...................................................................... 2

6 Conformance tests ............................................................................................................................... 5

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

6.2 V output function............................................................................................................................. 5

Split

6.3 Output voltage during low-power mode............................................................................................. 6

6.4 Internal resistance during low-power mode ...................................................................................... 6

6.5 Propagation delay during normal mode............................................................................................. 7

6.6 Wake-up filter time during low-power mode...................................................................................... 7

6.7 Bus driver symmetry during normal mode ........................................................................................ 7

6.8 Input leakage current, unpowered device.......................................................................................... 8

7 Electrical specification of high-speed medium access unit (HS-MAU)........................................... 8

7.1 Physical medium attachment sub layer specification ...................................................................... 8

7.2 CAN node............................................................................................................................................. 10

7.3 Medium dependent interface (MDI) specification, connector parameters.................................... 18

7.4 Physical medium specification ......................................................................................................... 18

Bibliography ..................................................................................................................................................... 20

© ISO 2007 – All rights reserved iii
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ISO 11898-5:2007(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.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. 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.

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.

ISO 11898-5 was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 3,

Electrical and electronic equipment.

ISO 11898 consists of the following parts, under the general title Road vehicles — Controller area network

(CAN):
⎯ Part 1: Data link layer and physical signalling
⎯ Part 2: High-speed medium access unit
⎯ Part 3: Low-speed, fault-tolerant, medium-dependent interface
⎯ Part 4: Time-triggered communication
⎯ Part 5: High-speed medium access unit with low-power mode
iv © ISO 2007 – All rights reserved
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ISO 11898-5:2007(E)
Introduction

ISO 11898 was first published as one document in 1993. It covered the CAN data link layer as well as the

high-speed physical layer.
In the reviewed and restructured ISO 11898 series:

⎯ Part 1 describes the data link layer including the logical link control (LLC) sub layer and the medium

access control (MAC) sub layer as well as the physical signalling (PLS) sub layer;

⎯ Part 2 defines the high-speed medium access unit (MAU);
⎯ Part 3 defines the low-speed fault-tolerant medium access unit (MAU);
⎯ Part 4 defines the time-triggered communication;
⎯ Part 5 defines the power modes of the high-speed medium access unit (MAU).
ISO 11898-1 and ISO 11898-2 have been cancelled and replaced ISO 11898:1993.
© ISO 2007 – All rights reserved v
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INTERNATIONAL STANDARD ISO 11898-5:2007(E)
Road vehicles — Controller area network (CAN) —
Part 5:
High-speed medium access unit with low-power mode
1 Scope

This part of ISO 11898 specifies the CAN physical layer for transmission rates up to 1 Mbit/s for use within

road vehicles. It describes the medium access unit functions as well as some medium dependent interface

features according to ISO/IEC 8802-2.

This part of ISO 11898 represents an extension of ISO 11898-2, dealing with new functionality for systems

requiring low-power consumption features while there is no active bus communication.

Physical layer implementations according to this part of ISO 11898 are compliant with all parameters of

ISO 11898-2, but are defined differently within this part of ISO 11898. Implementations according to this part

of ISO 11898 and ISO 11898-2 are interoperable and can be used at the same time within one network.

2 Normative references

The following referenced documents are indispensable for the application 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 7637-3, Road vehicles — Electrical disturbances from conduction and coupling — Part 3: Electrical

transient transmission by capacitive and inductive coupling via lines other than supply lines

ISO 11898-2:2003, Road vehicles — Controller area network (CAN) — Part 2: High-speed medium access

unit
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 11898-2 and the following apply.

3.1
VCC

〈CAN node〉 supply voltage of the physical layer used for the bus receiver, transmitter and optional split

termination voltage V during normal mode
Split
NOTE Typical voltage of VCC is 5 V.
3.2
split termination voltage
Split

〈CAN node〉 output voltage of split termination support output relative to ground signal of the module (GND)

© ISO 2007 – All rights reserved 1
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ISO 11898-5:2007(E)
3.3
propagation time
Prop

〈CAN node〉 signal propagation time measured from an edge at transmit data (TXD) input to the corresponding

edge on receive data (RXD) output of the MAU
3.4
wake-up filter time
Wake

〈CAN node〉 duration of a dominant signal on the bus lines CAN_H and CAN_L for forcing a wake-up to the

CAN NODE
3.5
wake-up pattern

〈CAN node〉 one or multiple consecutive dominant bus levels for at least t , each separated by a recessive

Wake
bus level

NOTE Figures within this part of ISO 11898 are using arrows as following: voltages + Æ –; currents flowing from the

positive to the negative pole.
4 Symbols and abbreviated terms

For the purposes of this document, the symbols and abbreviated terms given in ISO 11898-2 apply.

5 Functional description of medium access unit (MAU) with low-power mode
5.1 General

The following description is valid for a two-wire differential bus. The values of the voltage levels, the

resistances and the capacitances as well as the termination network are described in Clause 7.

5.2 Physical medium attachment sub layer specification
5.2.1 General

As shown in Figure 1 the bus line is terminated by termination network A and termination network B. These

terminations are intended to suppress reflections.

Besides this reflection-optimized termination structure, centralized single terminations are possible at limited

bit rates and topologies.
Figure 1 — Suggested electrical interconnection
2 © ISO 2007 – All rights reserved
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ISO 11898-5:2007(E)

Two different termination models are recommended within the high-speed medium access unit according to

Figures 1 and 2:
⎯ termination with a single resistor between CAN_H and CAN_L, and

⎯ split termination dividing the single resistor into two resistors with the same value in series connection,

while the centre tap is connected to a grounding capacitor and optionally to a dedicated split supply.

Key
1 physical layer

Figure 2 — Termination variants, single resistor termination and split termination

In order to support low-power functionality, two different modes of operation are defined as follows.

⎯ Normal mode: The behaviour during normal mode is described within ISO 11898-2.
⎯ Low-power mode: Described within this part of ISO 11898.
5.2.2 Bus levels during normal mode

The bus can have one of the two logical states: recessive or dominant (see Figure 3).

The bus is in the recessive state if the bus drivers of all CAN nodes are switched off. In this case, the mean

bus voltage is generated by the termination and by the high internal resistance of each CAN node’s receiving

circuitry. In the recessive state, V and V are fixed to a mean voltage level, determined by the bus

CAN_H CAN_L

termination. V is less than a maximum threshold. The recessive state is transmitted during bus idle or a

diff

recessive bit. Figure 3 illustrates the maximum allowed differential recessive bus voltage. Typically, the

differential voltage is about zero volts.

Optionally the recessive bus state may become stabilized making use of a dedicated split termination voltage

(V ). This optional output voltage of physical layer implementations according to this part of ISO 11898 may

Split

be optionally connected to the centre tap of the split termination resistors. Whenever the receiver of a physical

layer is not actively biasing towards 2,5 V, the optional V shall become floating.

Split

A dominant bit is sent to the bus if the bus driver of at least one unit is switched on. This induces a current

flow through the terminating resistors, and consequently a differential voltage between the two wires of the

bus. A differential voltage greater than a minimum threshold represents the dominant state. The dominant

state overwrites the recessive state, and is transmitted during a dominant bit.

The dominant and recessive states are detected by transforming the differential voltages of the bus to the

corresponding recessive and dominant voltage levels within the receive comparator.

During arbitration, various CAN nodes may simultaneously transmit a dominant bit. In this case, V exceeds

diff

the V seen during a single operation. Single operations means that the bus is driven by one CAN node only.

diff
© ISO 2007 – All rights reserved 3
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ISO 11898-5:2007(E)
5.2.3 Bus levels during low-power mode

During low-power mode, the bus drivers are entirely disabled. It is not possible to actively drive a differential

level to the bus lines using a physical layer within low-power mode. In contrast to the normal mode behaviour,

the bus wires shall be pulled to the ground signal of the module (GND) via the high-ohmic internal input

resistors R of the receiver. Thus, there is no active VCC supply required defining the bus levels during low-

power operation.

The optional split termination voltage (V ) is disabled here and shall behave high-ohmic (floating) in order

Split
not to pull the bus into a certain direction.

From a physical point of view, there are only the two defined operating conditions possible. The normal mode

with VCC/2 biasing whenever normal bus communication takes place and low-power mode with GND biasing

whenever the system becomes shutdown.
Key
1 normal mode
2 low-power mode
3 simplified transceiver bias implementation
Figure 3 — Physical bit representation and simplified bias implementation
5.2.4 Wake-up out of low-power mode

During low-power operation, a physical layer optionally shall monitor the bus lines CAN_H and CAN_L for

wake-up events. Implementations supporting this feature shall make use of a differential bus comparator

monitoring the bus line. A bus wake-up shall be performed if the bus shows one or multiple consecutive

dominant bus levels for at least t , each separated by a recessive bus level.
Wake
5.2.5 Systems with unpowered nodes

In order to allow undisturbed CAN communication in systems, which have a couple of nodes intentionally

unpowered (e.g. ignition key controlled modules), while other nodes continue to communicate normally, it is

important that these unpowered nodes affect the bus levels as little as possible. This requires that

transceivers, which are temporarily unpowered, show a lowest possible leakage current to the bus lines inside

the still communicating system. The lower the leakage current in the unpowered case, the better the system

performance in the permanently supplied part of the network.

Depending on the target application (permanently supplied or temporarily unsupplied) the maximum leakage

parameter according to Table 4 can be tolerated (permanently supplied nodes) or should be reduced as far as

possible (temporarily unsupplied nodes).
4 © ISO 2007 – All rights reserved
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ISO 11898-5:2007(E)

NOTE In contrast to a low-power mode, where the device is still supplied, unpowered means a physical

disconnection from the power supply.
6 Conformance tests
6.1 General

All conformance tests for normal mode of operation are specified in ISO 11898-2. Besides these tests, some

tests are added dealing with the optional V functionality and the low-power mode behaviour.

Split

The figures and the formulae shown within this clause indicate the principles of how the electrical parameters

specified in Clause 7 should be verified.
6.2 V output function
Split
6.2.1 General

V is an optional output voltage supporting recessive bus stabilization. When this function is implemented,

Split

the behaviour of that output shall be measured as shown within the following clauses.

6.2.2 V during normal mode
Split
The optional output V delivers an output voltage of VCC/2 during normal mode.
Split

According to Table 6, an output current of +500 µA to GND (Figure 4 schematic A) and −500 µA to VCC

(Figure 4 schematic B) shall be adjusted with the resistor R, while the output voltage V shall stay within the

Split
limits.

In unloaded condition (Figure 4 schematic C), the output voltage shall be checked according to Table 6 using

a load resistance of W 1 MΩ.
Figure 4 — Measurement of V during normal mode
Split
6.2.3 V during low-power mode
Split

The optional output V shall float during low-power mode (see Figure 5). The leakage current is defined in

Split
Table 6.
© ISO 2007 – All rights reserved 5
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ISO 11898-5:2007(E)
Figure 5 — Measurement of leakage current I during low-power mode
Split
6.3 Output voltage during low-power mode

During low-power mode, CAN_H and CAN_L shall be pulled towards GND using the internal input resistor R

of the bus receiver network (see Figure 6). Voltage levels at CAN_H and CAN_L shall be in accordance with

Table 8.
Figure 6 — Measurement of V and V during low-power mode
CAN_L CAN_H
6.4 Internal resistance during low-power mode

During low-power mode, CAN_H and CAN_L shall be pulled towards GND with the internal input resistor

network (see Figure 7), according to Table 9.
Figure 7 — Measurement of R during low-power mode

Applying a voltage U to the test circuit allows the calculation of R based on the voltage divider defined

Test in
with R as follows:
Test
R ×V
Test
R =
in_L,H
UV−
Test
6 © ISO 2007 – All rights reserved
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ISO 11898-5:2007(E)
6.5 Propagation delay during normal mode

In case of access to the pins RXD [Receive Data (serialized data)] and TXD [Transmit Data (serialized data)]

of a physical layer implementation, the signal propagation time shall be measured according to Figure 8.

Table 11 specifies the propagation time and defi
...

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