1、 WORLDWIDE ENGINEERING STANDARDS General Specification GMW3104 GMLAN Communication Strategy Specification Copyright 2013 General Motors Company All Rights Reserved July 2013 Page 1 of 52 1 Introduction Note: Nothing in this standard supercedes applicable laws and regulations. Note: In the event of c
2、onflict between the English and domestic language, the English language shall take precedence. 1.1 Scope. This specification establishes the communication strategy for the GM In-Vehicle Local Area Network (GMLAN) Subsystem. Implementation of this strategy is required for all Electronic Control Units
3、 (ECU) connected to the network. 1.2 Mission/Theme. The GMLAN subsystem shall provide a reliable, cost effective, flexible and modular way to handle information sharing between different ECUs in the vehicle through the means of a family of serial communication buses. GMLAN is scaleable to support th
4、e range from simple control modules up to highly complex units. The communication system also supports the transfer of diagnostic services and the transformation from and to a specified set of globally accepted standards for diagnostic tester access and communication. 1.3 Classification. Not applica
5、ble. 1.4 Requirement Wording Conventions. Within this document the following conventions are applied: The word “Shall” is used in the following ways: a. To state a binding requirement on the GMLAN network, or the nodes which comprise the network, which is verifiable by external manipulation and/or o
6、bservation of a node or the network. b. To state a binding requirement upon a nodes requirements document that is verifiable through a review of the document. The word “Must” is used in the following ways: a. To state a binding requirement upon nodes on the network that will have a corresponding nod
7、e requirements document. These requirements will be verified as part of the component verification. b. To characterize an expected behavior that is the natural consequence of another requirement in this document. The word “Should” denotes a preference or desired conformance. 2 References Note: Only
8、the latest approved standards are applicable unless otherwise specified. 2.1 External Standards/Specifications. ISO 11898 ISO-WD 15765-2 2.2 GM Standards/Specifications. GMW3089 GMW3122 GMW14241 GMW3110 GMW3173 3 Subsystem Definition The GM in vehicle Local Area Network (GMLAN) is to provide the cap
9、ability to transfer information between the different nodes on the vehicle, by a set of electrical wires, a serial communication bus. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from I
10、HS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW3104 Copyright 2013 General Motors Company All Rights Reserved July 2013 Page 2 of 52 3.1 Document Structure. There are two types of documents in GMLAN: General Specifications and Device Specifications. (See Figure A1). 3.1.1 General Specification. The ge
11、neral specifications establish the communications concept. For a given ECU, it is possible that not everything in the general specifications will apply. Figure 1: GMLAN Documents 3.1.2 Device Specification. The device specification is ECU specific. It contains: References to the optional parts of ge
12、neral specifications that applicable to the ECU. ECU specific information (e.g., signals and messages received by that ECU). 3.2 Overview. 3.2.1 GMLAN Buses. GMLAN provides a family of serial communication buses to enable Electronic Control Units (ECU) to communicate with each other. GMLAN comprises
13、 of three buses, a Low-speed bus, a Mid-speed bus, and a High-Speed bus, all of which are based on the Controller Area Network (CAN) communications protocol. The three buses are as follows: High-speed bus - typically used for sharing real time data such as driver-commanded torque, actual engine torq
14、ue, steering angle, etc. Mid-speed bus - typically used for infotainment applications (display, navigation, etc.) where the system response time demands that a large amount of data be transmitted in a relatively short amount of time, such as updating a graphics display. Copyright General Motors Comp
15、any Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW3104 Copyright 2013 General Motors Company All Rights Reserved July 2013 Page 3 of 52 Low-speed bus - typically used f
16、or operator controlled functions where the system response time requirements are of the order of 100 ms to 200 ms. Use of a given bus in a vehicle depends upon how feature/functions in that vehicle are partitioned among different ECUs. Figure 2 is an illustration of in-vehicle networking using the h
17、igh-speed link and the low-speed link. It should not be construed as actual vehicle wiring. D L CG3G1re mo t e a c c e s s t oGM L A N v ia G4G4N o n - GM L A N n e t wo rkG2s e rv ic e t o o lG1 - g a te w a y b e tw e e n GM L AN n e tw o r ks e .g . b e tw e e n l o w sp e e d n e tw o r k a n d
18、h i g h sp e e d n e tw o r kG2 - g a te w a y to a n o n - GM L A N p r o to co l u se d fo r d i a g n o sti c fu n cti o n se .g . b e tw e e n GM L AN a n d KW 2 0 0 0 p r o to co lG3 - g a te w a y to a n o n - GM L A N p r o to co l u se d fo r ve h i cl e fu n cti o n s e .g . b e tw e e n GM
19、 L AN a n d a n i n d u str y d e ve l o p e d e n te r ta i n m e n t b u sG4 - g a te w a y to p r o vi d e r e m o te a cce ss to GM L A Ne .g . b e tw e e n GM L AN a n d On sta r se r vi ce ce n te rb u s t e rmin a t io n b u s t e rmin a t io nFigure 2: GMLAN Buses 3.3 Communication. With res
20、pect to the International Organization for Standardization (ISO)/Open System Interconnection (OSI) reference model, communication is based on a layer model and consists of the physical layer, data link layer, transport layer, node management layer, network management layer and the interaction layer.
21、 This illustration (Figure 3) is intended to describe the hierarchy of a communication kernel. Figure 3: GMLAN Communication Kernel Concept Model I n t e r a c t ionL a y e rD a t a L ink L a y e rN e t w o r kL a y e rN o d eMan a g e men tP h y s ic a l L a y e r : C o mm u n ic a t ion sH a r d w
22、 a r eP h y s ic a l L a y e r : B u sN e t w o r kMan a g e men tAp p l i ca ti o nCopyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW3104
23、Copyright 2013 General Motors Company All Rights Reserved July 2013 Page 4 of 52 3.3.1 Interaction Layer. The interaction layer serves as the application program interface. It provides communication services to the application independent of the bus protocol and uses services of the transport layer
24、for communicating on the network. 3.3.2 Network Layer. The network layer transfers data packets up to 4095 bytes using services of the data link layer. It provides an unacknowledged transport service (1:N communication, 1:1 communication). If long messages have to be transferred over the network, th
25、e transport layer provides services for segmented data transfer. On the transmit side, the message is broken into segments, each segment being short enough to fit in a CAN frame. On the receive side, individual segments are assembled into a message. The network layer also provides connect setup and
26、flow control. 3.3.3 Data Link Layer. The data link layer provides services for the transfer of individual frames between nodes. It handles the protocol of the bus system (bit timing, arbitration, error detection, etc.) 3.3.4 Node Management Layer. The node management layer is used by the node to con
27、trol the start-up, shutdown and error handling for a node where these functions do not involve interaction with the other nodes of the network and, therefore, can be managed locally. 3.3.5 Network Management Layer. The network management layer is used to control the start-up, shutdown and error hand
28、ling for a network of nodes, where these functions involve interaction among the nodes and, therefore, have to be managed globally. 3.3.6 Physical Layer. The physical layer provides a method for converting the digital data symbols (1s and 0s) generated by the data link layer into electrical signals
29、transmitted on the communications medium. The Physical Layer includes the following. Transceiver: Electrical circuit that connects the protocol controller to the bus. Bus Loading: The electrical load, resistance and capacitance, on the bus line(s). Filter: Inductor to improve Electromagnetic Interfe
30、rence (EMI) immunity. Wiring: Physical media used to send the electrical signal. 3.4 Gateway Overview. Figure 4: GMLAN Gateway Principal Overview GMLAN consists of 1 to 3 subnets, the High-speed Bus, the Low-speed Bus, and the Mid-speed Bus. Despite the fact that networks are designed such that the
31、bulk of the signals will stay in their local network, some signals will have to be transferred outside the local network. Gateway nodes perform this function. A Gateway node is connected to at least 2 buses and will interact with each network according to its message strategy and transmission models
32、 (see Figure 4). These Gateway nodes normally carry out several application tasks where the Gateway is merely one of them. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM W
33、ORLDWIDE ENGINEERING STANDARDS GMW3104 Copyright 2013 General Motors Company All Rights Reserved July 2013 Page 5 of 52 The Gateway interacts with the bus kernels Interaction Layers (IL) and performs some or all of the following services: a. Transfer wake up requests to other networks; b. Transfer V
34、irtual Network (VN) information to other networks; c. Transfer signals between networks; d. Support signal parameter processing (event generation, data conversion, data filtering, etc.); e. Transfer block information with Unacknowledged Segmented Data Transfer (USDT) protocol. 4 Requirements Note: N
35、umerous requirements in this section rely on the concept of timers. For the purposes of these requirements, timers should be considered to be “count-down” timers that halt at a value of zero. The terms “set” and “reset” will be used to describe the operation of establishing a timer value, and the te
36、rm “clear” will be used to describe the operation of setting the timer to a value of zero. The term “halt” describes the timer operation which causes the timer to freeze at its current value. The actual timer maintenance and update processes are not specified. 4.1 Interaction Functions. Communicatio
37、n between nodes on the GMLAN shall consist of standard frames governed by approved interface specifications, and of vehicle specific frames consisting of approved standard signals. 4.1.1 Message Transmission Models. Communication between nodes on the GMLAN shall consist exclusively of the message tr
38、ansmission models described in the following sections. Signals are associated with Virtual Networks and they shall only be transmitted while the Virtual Network is active. 4.1.1.1 Periodic Transmit Model. 4.1.1.1.1 Periodic messages shall be transmitted at a fixed repetition rate (see Figure 5) whil
39、e an associated Virtual Network is active. 4.1.1.1.2 Periodic message interval accuracy shall be within 10% of the repetition rate measured with the device in isolation. Note: Nodes should spread their periodic messages to avoid burst situations, if required by the Component Technical Specification
40、(CTS). Figure 5: Periodic Transmit Model 4.1.1.2 Event Transmit Model. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW3104 Copyright 201
41、3 General Motors Company All Rights Reserved July 2013 Page 6 of 52 4.1.1.2.1 Event messages shall be sent in response to an internal or external event. See Figure 6. Note: In some cases, the application will queue the event messages at periodic intervals while an enabling condition persists. Though
42、 the resulting pattern is often referred to as “Periodic-when-Enabled”, it is not a fundamentally different transmit model from the Event Transmit Model. 4.1.1.2.2 Consecutive transmissions of the same message shall be separated by a specified minimum time known as the Min Update Time. Note: It is i
43、mportant to note that the Min Update Time is applied on a message-by-message basis. Sometimes multiple signals in a single message have launch criteria associated with them, and immediately following a message transmission satisfying one signals launch condition a different signal meets a launch con
44、dition. The Min Update Time should be observed between these two successive transmissions. A similar circumstance can happen with a single signal, if it has multiple launch criteria. In particular, this is possible if a signal is contained in a single message that supports two different Virtual Netw
45、orks. 4.1.1.2.3 All message transmission triggers which occur before the Min Update Time has elapsed shall be satisfied with a single transmission at the end of the update time. Figure 6: Event Transmit Model 4.1.1.3 Periodic with Event Transmit Model. The Periodic with Event Transmit Model consists
46、 of an Event Transmit Model superimposed on a Periodic Transmit Model except that the Min Update Time is enforced between two consecutive transmissions, regardless of which of the superimposed models triggers it. (See Figure 7). 4.1.1.3.1 Consecutive transmissions of the same message shall be separa
47、ted by a specified minimum time known as the Min Update Time. 4.1.1.3.2 All message transmission triggers which occur before the Min Update Time has elapsed shall be satisfied with a single transmission at the end of the update time. 4.1.1.3.3 The Min Update Time shall be less than the period minus
48、its negative tolerance. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW3104 Copyright 2013 General Motors Company All Rights Reserved Ju
49、ly 2013 Page 7 of 52 Figure 7: Periodic with Event Transmit Model 4.1.2 Signal Data Sampling. Message transmissions must include the most recently available signal data. Multiple byte signals should be retrieved without the possibility of an interrupt occurring between retrieval of each individual byte. The GMLAN handler shall allow application to retrieve/store the constitu
