ISO 9141:1989 Road vehicles — Diagnostic systems — Requirements for interchange of digital information
2 Normative references
ISO 4092 : 1988, Road vehicles — Diagnostic systems for motor vehicles — Vocabulary.
ISO/TR 7637-0 : 1984, Road vehicles — Electrical interference by conduction and coupling — Part 0: General and definitions.
3 Definitions
For the purposes of this International Standard, the following definitions apply.
3.1 inspection
See ISO 4092.
3.2 test
See ISO 4092.
3.3 diagnosis
See ISO 4092.
3.4 diagnostic tester
See ISO 4092.
This non-built-in equipment may be used in the vehicle.
3.5 system
Assemblage of components performing a specific function, for example an assemblage of an ECU with its associated sensors, actuators and interconnections.
3.6 ECU
Abbreviation of Electronic Control Unit.
3.7 bus
One or more conductors connecting two or more ECUs together with the purpose of communicating with the test equipment.
3.8 NRZ
Abbreviation of Non-Retum-to Zero — a method of representing binary signals in which there is no change of signal levels between two successive bits of the same logic level.
3.9 baud rate
Number of binary elements of information transmitted per second on one line.
3.10 LSB
Abbreviation of Least Significant Bit.
3.11 MSB
Abbreviation of Most Significant Bit.
3.12 initialization
Process to activate an ECU for starting communication.
3.13 key words
Identifier of a set of specifications for the subsequent serial communication.
This set of specifications defines:
— the specific function of each communication line;
— the format of the digital information such as the protocol, number and meaning of each of the words exchanged; and
— if a redefinition is desired, the format of data such as baud rate, data coding, word length.
3.14 header
First group of serial data transmitted to the diagnostic tester after initialization (if required) before further data exchange commences.
The header consists of
— baud rate synchronization pattern;
— key words.
3.15 bit time
Duration of one unit of information.
content
Foreword
Introduction
1 Scope
2 Normative references
3 Definitions
4 General configurations
5 Signal and communication specifications
5.1 Signal
5.2 Communication
6 Initialization of the ECU prior to serial communication
7 Header
7.1 Purpose
7.2 Baud rate synchronization pattern
7.3 Key word format
7.4 Key word assignation
7.5 Time requirements
8 Requirements of the diagnostic tester
8.1 Standard connector
8.2 Input and output lines
8.3 Facilities provided by the diagnostic tester for the ECU initialization
8.4 Minimum functional capabilities
8.5 Electrical specification for the diagnostic tester of 12 V vehicle battery voltage systems (values in parentheses refer to diagnostic tester for 24 V vehicle battery voltage systems)
9 Requirements of the ECU
9.1 Input and output lines
9.2 Electrical specifications for ECUs in 12 V vehicle battery systems (values in parentheses refer to ECUs in 24 V vehicle battery systems)
9.3 Recognition of an initialization address10 Requirements of the wiring