SAE J 1939-15-2015 Physical Layer 250 Kbps Un-Shielded Twisted Pair (UTP).pdf

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4、70 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/J1939/15_201508 SURFACE VEHICLE RECOMMENDED PRACTICE J1939-15 AUG2015 Issued 200

5、3-11 Revised 2015-08 Superseding J1939-15 MAY2014 Physical Layer, 250 Kbps, Un-Shielded Twisted Pair (UTP) RATIONALE Document is revised to correct a typographical error in a reference to ISO 11898, and to modify Appendix B for consistency with SAE J1939-11. FOREWORD The set of SAE J1939 Recommended

6、 Practice documents define a high speed ISO 11898 CAN protocol based communications network that can support real-time closed loop control functions, simple information exchanges, and diagnostic data exchanges between Electronic Control Units (ECUs) physically distributed throughout the vehicle. The

7、 SAE J1939 communications network is developed for use in heavy-duty environments and suitable for use in horizontally integrated vehicle industries. The physical layer aspects of SAE J1939 reflect its design goal for use in heavy-duty environments. Horizontally integrated vehicles involve the integ

8、ration of different combinations of loose package components, such as engines and transmissions, which are sourced from many different component suppliers. The SAE J1939 common communication architecture strives to offer an open interconnect system that allows the ECUs associated with different comp

9、onent manufacturers to communicate with each other. The SAE J1939 communications network is intended for light-duty, medium-duty, and heavy-duty vehicles used on-road or off-road, and for appropriate stationary applications which use vehicle derived components (e.g. generator sets). Vehicles of inte

10、rest include, but are not limited to, on-highway and off-highway trucks and their trailers, construction equipment, and agricultural equipment and implements. This set of SAE Recommended Practices has been developed by the SAE Truck and Bus Control and Communications Network Committee of the SAE Tru

11、ck and Bus Electrical and Electronics Steering Committee. The SAE J1939 communications network is defined using a collection of individual SAE J1939 documents based upon the layers of the Open System Interconnect (OSI) model for computer communications architecture. These SAE J1939 documents are int

12、ended as a guide toward standard practice and are subject to change to keep pace with experience and technical advances. SAE INTERNATIONAL J1939-15 AUG2015 Page 2 of 19 TABLE OF CONTENTS 1. SCOPE 3 2. REFERENCES 3 2.1 Applicable Documents 3 2.1.1 SAE Publications . 3 2.2 Related Publications . 4 2.2

13、.1 ISO Publications 4 3. NETWORK PHYSICAL DESCRIPTION . 4 3.1 Physical Layer . 4 3.2 Physical Media 4 3.3 Differential Voltage 4 3.4 Bus Levels . 4 3.5 Bus Levels During Arbitration . 4 3.6 Common Mode Bus Voltage Range . 4 3.7 Bus Termination 5 3.8 Internal Resistance . 5 3.9 Differential Internal

14、Resistance . 5 3.10 Internal Capacitance . 5 3.11 Differential Internal Capacitance . 5 3.12 Bit Time . 5 3.13 Internal Delay Time . 5 3.14 CAN Bit Timing Requirements 5 4. FUNCTIONAL DESCRIPTION . 6 5. ELECTRICAL SPECIFICATION . 6 5.1 Electrical Data . 6 5.1.1 Electronic Control Unit 6 5.1.2 Bus Vo

15、ltages - Operational . 7 5.1.3 Electrostatic Discharge (ESD) 7 5.1.4 Example Physical Layer Circuits . 7 5.2 Physical Media Parameters 7 5.2.1 Bus Line 9 5.2.2 Topology . 9 5.2.3 Terminating Resistor . 10 5.2.4 Shield Termination 11 5.2.5 ECU Type I and Type II Markings . 11 5.3 Connector Specificat

16、ions 11 5.3.1 Connector Electrical Performance Requirements . 12 5.3.2 Connector Mechanical Requirements . 12 6. CONFORMANCE TESTS . 12 6.1 Recessive Output of the ECUs . 12 6.2 Internal Resistance of CAN_H and CAN_L 12 6.3 Internal Differential Resistance . 12 6.4 Recessive Input Threshold of an EC

17、U 12 6.5 Dominant Output of an ECU . 12 6.6 Dominant Input Threshold of an ECU . 12 6.7 Internal Delay Time . 12 7. DISCUSSION OF BUS FAULTS 12 7.1 Loss of Connection to Network . 12 7.2 Node Power or Ground Loss 13 7.3 Unconnected Shield 13 7.4 Open and Short Failures . 13 SAE INTERNATIONAL J1939-1

18、5 AUG2015 Page 3 of 19 8. NOTES 13 8.1 Revision Indicator 13 Figure 1 Cable cross-section and bend radius 9 Figure 2 Wiring network topology (type I ECUS only) . 9 Figure 3 Wiring network topology (one type II ECU installed) 10 Figure 4 Wiring network topology (two type II ECUS installed) 10 Figure

19、5 An example of SAE J1939-11 connector usage in a SAE J1939-15 network 11 Figure A1 Example of preferred signal rise/fall waveforms . 14 Figure B1 Cable termination 3 cavity connector 15 Figure B2 Cable termination of a typical 2 cavity connector . 15 Figure B3 Typical finished assembly . 15 Figure

20、C1 Cable splice . 16 Figure C2 Sealed cable splice-finished assembly . 16 Figure D1 Cable splice . 17 Figure D2 Cable splice-finished assembly . 17 Figure F1 SAE J1939-11 tool connected to the SAE J1939-15 network 19 Figure F2 ECU (using SAE J1939-11 pigtail and 3-pin connector) connected to the SAE

21、 J1939-15 network 19 Table 1 AC parameters of an ECU disconnected from the bus line 6 Table 2 Physical media parameters for un-shielded twisted pair cable . 8 Table 3 Network topology parameters . 10 Table E1 Comparison SAE J1939-15 vs SAE J1939-11 . 18 1. SCOPE This document describes a physical la

22、yer utilizing Unshielded Twisted Pair (UTP) cable with extended stub lengths for flexibility in ECU placement and network topology. Also, connectors are not specified. CAN controllers are now available which support the newly introduced CAN Flexible Data Rate Frame format (known as “CAN FD”). These

23、controllers, when used on SAE J1939-15 networks, must be restricted to use only the Classical Frame format compliant to ISO 11898-1 (2003). These SAE Recommended Practices are intended for light- and heavy-duty vehicles on- or off-road as well as appropriate stationary applications which use vehicle

24、 derived components (e.g., generator sets). Vehicles of interest include but are not limited to: on- and off-highway trucks and their trailers; construction equipment; and agricultural equipment and implements. 2. REFERENCES General information regarding this series of recommended practices is found

25、 in SAE J1939. 2.1 Applicable Documents The following publications form a part of this specification to the extent specified herein. Unless otherwise indicated, the latest issue of SAE publications shall apply. 2.1.1 SAE Publications Available from SAE International, 400 Commonwealth Drive, Warrenda

26、le, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org. SAE J1128 Low-Voltage Primary Cable SAE J1939-11 Physical Layer, 250 Kbps, Twisted Shielded Pair SAE J1939-13 Off-Board Diagnostic Connector SAE INTERNATIONAL J1939-15 AUG2015 Page 4 of 19 2.2 Re

27、lated Publications The following publications are provided for information purposes only and are not a required part of this SAE Technical Report. 2.2.1 ISO Publications Available from American National Standards Institute, 25 West 43rd Street, New York, NY 10036-8002, Tel: 212-642-4900, www.ansi.or

28、g. ISO 11898 Road vehicles - Interchange of digital information - Controller Area Network (CAN) for high speed communication. 3. NETWORK PHYSICAL DESCRIPTION The SAE J1939-15 physical layer has the same characteristics as the SAE J1939-11 physical layer except as described in this document. It is th

29、e responsibility of the vehicle manufacturer to determine when the SAE J1939-15 physical layer should be used versus the SAE J1939-11 physical layer. Appendix E, Table E1 contains a comparison of SAE J1939-15 characteristics versus SAE J1939-11. 3.1 Physical Layer The physical layer is a realization

30、 of an electrical connection of a number of ECUs (Electronic Control Units) to a network. The total number of ECUs will be limited by electrical loads on the bus line. Stubs, being un-terminated, create signal reflections on the network. A total of up to 10 ECUs on a network segment is considered to

31、 present low risk of coincident reflections of sufficient magnitude to create bit errors and error frames. Up to 30 ECUs may be connected on a network segment if special care is taken to vary the spacing between stubs to avoid the effects of reflections. Consideration must also be given to EMC perfo

32、rmance which may be affected by the total stub length. The SAE J1939-15 network was designed as a reduced SAE J1939-11 network for connecting standard ECUs on a vehicle (e.g., Engine, ABS, Transmission). The SAE J1939-15 network allows the vehicle integrator to design a reduced network to meet desig

33、n and cost goals with comparable performance to the SAE J1939-11 network. 3.2 Physical Media This document defines a physical media of jacketed un-shielded twisted pair (UTP). These 2 wires have a characteristic impedance of 120 : and are symmetrically driven with respect to the electrical currents.

34、 The designations of the individual wires are CAN_H and CAN_L. The names of the corresponding pins of the ECUs are also denoted by CAN_H and CAN_L, respectively. 3.3 Differential Voltage Same as the SAE J1939-11 physical layer. 3.4 Bus Levels Same as the SAE J1939-11 physical layer. 3.5 Bus Levels D

35、uring Arbitration Same as the SAE J1939-11 physical layer. 3.6 Common Mode Bus Voltage Range Same as the SAE J1939-11 physical layer. SAE INTERNATIONAL J1939-15 AUG2015 Page 5 of 19 3.7 Bus Termination The bus is electrically terminated at each end with a load resistor denoted by RL. SAE J1939-11 re

36、quires that RL be located external to ECUs. This Recommended Practice, J1939-15, defines Type I and Type II ECUs. Type I ECUs shall not contain the bus termination resistor RL. Type II ECUs shall contain the bus termination resistor and if used shall be located only at one or both ends of an SAE J19

37、39-15 network. Type II ECUs shall be clearly marked as specified in Section 5.2.5. 3.8 Internal Resistance Same as the SAE J1939-11 physical layer. 3.9 Differential Internal Resistance Same as the SAE J1939-11 physical layer. 3.10 Internal Capacitance Same as the SAE J1939-11 physical layer. 3.11 Di

38、fferential Internal Capacitance Same as the SAE J1939-11 physical layer. 3.12 Bit Time Same as the SAE J1939-11 physical layer. 3.13 Internal Delay Time For those networks utilizing a diagnostic stub which may exceed 3 meters, ECU delay time is reduced to 0.7 s. 3.14 CAN Bit Timing Requirements The

39、CAN bit timing requirements for the SAE J1939-15 are the same as the SAE J1939-11 physical layer, except Table 1 below should be used, which includes the Signal Rise / Fall Time parameter. If a discrete circuit is used, the Signal Rise / Fall Time should be adjusted per Table 1, Note 2. Some transce

40、iver chips offer faster rise and fall times than are given in Table 1 without an increase in EMI. If emissions control or slope control is not integral to the transceiver, EMI performance must be equivalent. The Signal Rise / Fall Time parameter has been included for clarity and to improve the Elect

41、romagnetic Compatibility (EMC) of the physical layer. The primary parameter for electromagnetic emission is the unbalance of the signals at CAN_H and CAN_L. To verify that the signals are balanced, the maximum voltage imbalance between CAN_H and CAN_L should not exceed 10 mVpp. The differential volt

42、age can be measured with ac-coupling and an oscilloscope: CAN_H minus CAN_L inverted. SAE INTERNATIONAL J1939-15 AUG2015 Page 6 of 19 Table 1 - AC PARAMETERS OF AN ECU DISCONNECTED FROM THE BUS LINE Parameter Symbol Min Nom Max Unit Conditions Bit time 1)tB3.998 4.000 4.002 s 250 Kbit/s Internal Del

43、ay Time 2)tECU0.0 0.7 s Internal Capacitance3) Cin0 50 100 pF 250 Kbit/s for CAN_H and CAN_L relative to Ground Differential Internal Capacitance 3) Cdiff0 25 50 pF Available Time 4)tavail2.5 s 40 m bus length Signal Rise, Fall Time 5)tR, tF 200 500 ns measured from 10% to 90% of the signal 1)Includ

44、ing initial tolerance, temperature, aging, etc. 2)The value of tECUhas to be guaranteed for a differential voltage of Vdiff= 1.0V for a transition from recessive to dominant and of Vdiff= 0.5V for a transition from dominant to recessive. With the bit timing from the example of note 1, a CAN-Interfac

45、e delay of 500 ns is possible (controller not included) with a reserve of about 300 ns. This allows slower/longer slopes (R3 and R4 in Figures A.1 and A.2) and input filtering (R5, R6, C1, C2 in Figures A.1 and A.2). It is recommended to use this feature due to EMC. (See J1939-11 Appendix A for figu

46、res.) The minimal internal delay time may be zero. The maximum tolerable value is determined by the bit timing and the bus delay time. 3)In addition to the internal capacitance restrictions a bus connection should also have an inductance as low as possible. The minimum values of Cinand Cdiffmay be 0

47、, the maximum tolerable values are determined by the bit timing and the network topology parameters L and d (see Table 3). Proper functionality is guaranteed if occurring cable resonant waves do not suppress the dominant differential voltage level below Vdiff= 1V and do not increase the recessive di

48、fferential voltage level above Vdiff= 0.5V at each individual ECU (see J1939-11 Tables 3 and 4). 4)The available time results from the bit timing unit of the protocol IC. For a typical example, this time in most controller ICs corresponds to TSEG1. Due to mis-synchronization it is possible to lose t

49、he length of SJW. So the available time (tavail) with one mis-synchronization is TSEG1-SJW ms. A tq time of 250 ns and SJW = 1 tq, TSEG1 = 13 tq, TSEG2 = 2tq results in tavail= 3.00 Ps. 5)A signal rise/fall time between 200-500 ns is required for the J1939-15 network if using adjustable circuits. Signal rise/fall times closer to 500 ns are preferred. Slower/longer signal rise/fall times improve the electromagnetic compatibility