LIN Network for Vehicle Applications
|Publication Date:||1 August 2004|
This document covers the requirements for SAE implementations based on LIN 2.0. Requirements stated in this document will provide a minimum standard level of performance to which all compatible ECUs and media shall be designed. This will assure full serial data communication among all connected devices regardless of supplier.
The goal of SAE J2602 is to improve the interoperability and interchangeability of LIN devices within a network by resolving those LIN 2.0 requirements that are ambiguous, conflicting, or optional. Moreover, SAE J2602 provides additional requirements that are not present in LIN 2.0 (e.g., fault tolerant operation, network topology, etc.).
This document is to be referenced by the particular vehicle OEM component technical specification that describes any given ECU in which the single wire data link controller and physical layer interface is located. Primarily, the performance of the physical layer is specified in this document. ECU environmental and other requirements, when provided in the component technical specification, shall supercede the requirements of this document.
The intended audience includes, but is not limited to, ECU suppliers, LIN controller suppliers, LIN transceiver suppliers, component release engineers and vehicle system engineers.
This serial data link network is intended for use in applications where high data rate is not required and a lower data rate can achieve cost reductions in both the physical media components and in the microprocessor and/or dedicated logic devices (ASICs) which use the network.
LIN is a single wire, low cost, Class A communication protocol. LIN is a master-slave protocol, and utilizes the basic functionality of most Universal Asynchronous Receiver Transmitter (UART) or Serial Communication Interface (SCI) devices as the protocol controllers in both Master and Slave devices. To meet the target of "Lower cost than either an OEM proprietary communications link or CAN link" for low speed data transfer requirements, a single wire transmission media based on the ISO 9141 specification was chosen. The protocol is implemented around a UART/SCI capability set, because the silicon footprint is small (lower cost), many small microprocessors are equipped with either a UART or SCI interface (lower cost), and the software interface to these devices is relatively simple to implement (lower software cost). Finally, the relatively simplistic nature of the protocol controller (UART/SCI) and the nature of state-based operation, enable the creation of Application Specific Integrated Circuits (ASICs) to perform as input sensor gathering and actuator output controlling devices, in the vein of Mechatronics.
All message traffic on the bus is initiated by the Master device. Slave devices respond to commands and requests from the Master. Since the Master initiates all bus traffic, it follows that the Slaves cannot communicate unless requested by the Master. However, Slave devices can generate a bus wakeup, if their inherent functionality requires this feature.
The "LIN Consortium" developed the set of LIN specifications. The Consortium is a group of automotive OEMs, semiconductor manufacturers, and communication software and tool developers. The LIN specification set is "released" by the LIN Steering Committee, a closed subset of the members. Associate Consortium members contribute to the formation of the specifications through participation in LIN Work Groups; however, the direction of the Work Groups and the final released content of the specifications is the responsibility of the LIN Steering Committee.
The LIN Specifications contain more than just a definition of the LIN protocol and physical layer. In addition, a Work Flow Process, Diagnostics and Configuration methods, definition of an Application Program Interface (API), file structures for a Node Capability File (NCF) and a LIN Description File (LDF) and semantics are identified as required (mandatory in all implementations). However, since there is a great deal of flexibility in the protocol and physical layer, applicability of these specifications to J2602 networks will be further specified in this document.
Relationship to the LIN Specifications (ref Section 2.6, LIN 2.0 Specification Package)
As described in the LIN Specification Package, the LIN 2.0 protocol specification suite consists of seven documents:
LIN SPECIFICATION PACKAGE
The LIN Specification Package provides an overview of the LIN Protocol, its features, and work flow. This includes the Revision History, LIN Overview and Glossary.
LIN PHYSICAL LAYER SPECIFICATION
The LIN Physical Layer Specification describes the physical layer, including bit rate, clock tolerances, etc.
LIN PROTOCOL SPECIFICATION
The LIN Protocol Specification describes the data link layer of LIN.
LIN DIAGNOSTIC AND CONFIGURATION SPECIFICATION
The LIN Diagnostic and Configuration Specification describes the services that can/may be layered on top of the data link layer to provide for diagnostic messages and node configuration.
LIN API SPECIFICATION
The LIN API Specification describes the interface between the network and the application program, including the diagnostic module.
LIN CONFIGURATION LANGUAGE SPECIFICATION
The LIN Configuration Language Specification describes the format of the LIN description file, which is used to configure the complete network and serve as a common interface between the OEM and the suppliers of the different network nodes, as well as an input to development and analysis tools.
LIN NODE CAPABILITY LANGUAGE SPECIFICATION
The LIN Node Capability Language Specification describes a format used to describe off-the-shelf slave nodes that can be used with a system definition tool to automatically create LIN Description Files.
The remainder of this document (SAE J2602) will directly reference these LIN specifications.