SAE J 2366-1L-2001 ITS Data Bus - Low Impedance Stereo Audio (LISA).pdf

1、SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirelyvoluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefro

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3、/www.sae.orgCopyright 2001 Society of Automotive Engineers, Inc.All rights reserved. Printed in U.S.A.SURFACEVEHICLE400 Commonwealth Drive, Warrendale, PA 15096-0001RECOMMENDEDPRACTICEJ2366-1LISSUEDNOV2001Issued 2001-11ITS Data BusLow Impedance Stereo Audio (LISA)TABLE OF CONTENTS1. Scope . 22. Refe

4、rences . 22.1 Applicable Publications 22.1.1 SAE Publications 22.2 Related Publications . 22.2.1 SAE Publications 23. Definitions. 23.1 Audio Arbitration . 23.2 IDB-C 23.3 ITS 23.4 LISA 23.5 Receiver . 23.6 Transmitter . 24. The LISA Bus . 34.1 Transmitter . 34.1.1 Number of Transmitters 34.1.2 Tran

5、smitter Output . 34.2 Receiver . 44.3 Bus Load Resistor 44.4 LISA Connections . 4Appendix A LISA Circuit Examples 5A.1.1 Transmitter Circuit 5A.1.2 Receiver Circuit 6A.1.3 Transceiver Circuit 7A.1.4 Grounding Example 8Figure A1 Example Transmitter Circuit . 5Figure A2 Example Receiver Circuit . 6Fig

6、ure A3 Example Transceiver Circuit. 7Figure A4 System Grounding Example. 8SAE J2366-1L Issued NOV2001-2-Table 1 Transmitter Types and Usage Profiles .3Table 2 Transmitter Parameters 4Table 3 Receiver Parameters 41. ScopeThis SAE Recommended Practice describes the Low Impedance Stereo Audio (LISA) bu

7、s, whichmay be used in conjunction with the Physical Layer of the IDB-C, as described in SAE J2366-1. The audioarbitration messages used to control access to the LISA bus are specified in SAE J2366-7.The IDB-C is a non-proprietary virtual token passing bus, designed to allow disparate consumer, vehi

8、cle, andcommercial electronic components to communicate and share information. 2. References2.1 Applicable PublicationsThe following publications form a part of this specification to the extent specifiedherein. Unless otherwise indicated, the latest issue of SAE publications shall apply.2.1.1 SAE PU

9、BLICATIONSAvailable from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001, or http:/www.sae.org.SAE J2366-1ITS Data BusPhysical LayerSAE J2366-7ITS Data BusApplication Message Layer2.2 Related Publications2.2.1 SAE PUBLICATIONSAvailable from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-00

10、01, or http:/www.sae.org.SAE J2355ITS Data BusArchitecture Reference Model Information ReportSAE J2366-2ITS Data BusLink LayerSAE J2366-4ITS Data BusThin Transport LayerSAE J2590PMODE for In-Vehicle Networks3. Definitions3.1 Audio ArbitrationAudio Arbitration is the process through which a Transmitt

11、er requests and is grantedpermission to generate audio output onto the LISA bus. When used with the IDB-C, the Audio Arbitrationmechanism and required messages are defined in SAE J2366-7.3.2 IDB-CThe IDB-C is a member of the ITS Data Bus (IDB) family of networks, defined by the SAE J2366series of do

12、cuments.3.3 ITS Intelligent Transportation Systems3.4 LISALow Impedance Stereo Audio the subject of this document.3.5 ReceiverA Receiver is a device capable of accepting an analog audio input signal, e.g., audio amplifier,memo recorder.3.6 TransmitterA Transmitter is a device capable of generating a

13、n analog audio signal, e.g., CD-changer,wireless phone, text-to-speech synthesizer.SAE J2366-1L Issued NOV2001-3-4. The LISA BusThe LISA bus is designed to allow multiple Transmitters and Receivers to be “bussed” on asingle unshielded twisted pair (UTP). One UTP is required for each LISA channel. A

14、stereo configurationwould therefore include 2 UTPs. Additional UTPs can be used for additional channels, as required. The LISAbus allows summing (mixing) of multiple Transmitters and Receivers, if desired, and is designed to becompliant with typical automotive EMC requirements.When used with IDB-C,

15、the Audio Arbitration mechanism defined in SAE J2366-7 controls access to the LISAbus.Appendix A shows examples of a LISA Transmitter, Receiver, and Transceiver circuit, and also provides anexample of an overall system grounding method that can help to reduce interference and ground potentialissues.

16、4.1 TransmitterA Transmitter always presents high impedance to the LISA bus, regardless of whether it isactually generating any audio output (Active) or not (Inactive). Transmitters fall into the categories shown inTable 1:4.1.1 NUMBER OF TRANSMITTERSThe number of Active Transmitters is limited by t

17、he Receiver input level and thetype of audio transmitted by each Transmitter. It is theoretically possible to have 16 Active Transmittersproviding that the Receiver input is not overloaded or the effects of clipping are not considered objectionable.The bus is specified such that it is possible to ha

18、ve one full volume Type 1 or Type 2 source and one fullvolume Type 3 source Active at the same time. Additional sources or alternate combinations can besupported by reducing the lower priority sources to low volume or muted states.It is the responsibility of the audio arbiter to manage the output le

19、vel of the Transmitters such that the totalsignal level on the bus is within the valid range and the final audio output is not objectionable to the listener. 4.1.2 TRANSMITTER OUTPUTTransmitters must operate in a high impedance state. Transmitters shall not causeaudible noise or attenuation when the

20、y join the LISA bus or when powering up.Transmitters shall have single ended high impedance current drive characteristics to avoid back-loadingactive signals on the bus. Transmitter parameters are shown in Table 2.Transmitters may be Active (generating audio content) or Inactive (not generating audi

21、o content). The stateshall be controlled by the Audio Arbitration scheme defined in SAE J2366-7. Each Transmitter shall support at least two output levels: High (full volume) and Muted. An additional Lowvolume output level should be supported, but may not make sense for all nodes (e.g., a backup war

22、ning aid).Additional levels may be supported at the discretion of the device manufacturer.TABLE 1TRANSMITTER TYPES AND USAGE PROFILESCategory Name DescriptionType 1 Priority This category includes devices that would override the entertainment content for some period of time. Examples include cell ph

23、ones, route guidance instructions, and driver information (voice alerts).Type 2 Entertainment This category includes devices such as CD players, radios, talking books, and other similar devices that generate continuous audio content.Type 3 Alert This category includes chimes, alerts, and other audio

24、 signals, that are very short in duration and are typically time sequenced apart.SAE J2366-1L Issued NOV2001-4-4.2 ReceiverSince +VBatt is always present on the IDB-C harness, to minimize any audio noise, the Receivershould disable its input while powering up and when joining the LISA bus. Receiver

25、parameters are describedin Table 3.4.3 Bus Load ResistorFor current mode operation, a 600 resistor is connected across the bus pairs on eachLISA channel. To remove any high frequency noise that might have been induced by outside devices, a0.0068 F capacitor should be inserted in parallel with the lo

26、ad resistor, as shown in Figure A4. A masterground point must be established to the vehicle chassis ground on the un-driven side of the 600 resistor (seeFigure A4).In an IDB-C implementation, the LISA bus is typically connected to the Vehicle Services Interface (orGateway), which connects the IDB-C

27、to the OEM-proprietary vehicle bus, and converts the LISA audio to thatrequired to feed the OEM entertainment radio. In this type of installation, the load resistor and filter capacitorwill typically reside in the Gateway.4.4 LISA ConnectionsWhen used with the IDB-C, the Vehicle Connector defined in

28、 SAE J2366-1 canaccommodate up to three LISA channels. The physical design and dimensions of the Vehicle Connector, andthe LISA bus signal pin assignments are specified in SAE J2366-1. PREPARED BY THE SAE ITS DATA BUS COMMITTEETABLE 2TRANSMITTER PARAMETERSParameter Minimum MaximumNumber of Active Tr

29、ansmitters 0Transmitter output impedance in Active, Inactive, or Low states 500 kTransmitter signal level measured at the LISA bus connection with source at full volume1.3 VrmsTransmitter signal level measured at the LISA bus connection with source at Low volume0.65 VrmsTransmitter signal level meas

30、ured at the LISA bus connection with source Muted0 VrmsTABLE 3RECEIVER PARAMETERSParameter Minimum MaximumNumber of Receivers 16Receiver input impedance 500 kReceiver input level 2 VrmsSAE J2366-1L Issued NOV2001-5-APPENDIX ALISA CIRCUIT EXAMPLESA.1 The following circuit diagrams show how LISA Trans

31、mitters, Receivers, and Transceivers may be built. Theseare provided as examples only and are not guaranteed to meet all the requirements of this specification.In all circuit diagrams, it is assumed that the node will have a means for controlling the FET switches shown.The HC series 4066 FET switch

32、available from Toshiba and others exhibits the low on resistance desired.A.1.1 Transmitter CircuitThe circuit shown in Figure A1 applies to a device that is only capable of generatingaudio output, e.g., a CD player, or text-to-speech synthesizer.FIGURE A1EXAMPLE TRANSMITTER CIRCUITSAE J2366-1L Issue

33、d NOV2001-6-A.1.2 Receiver CircuitThe circuit shown in Figure A2 applies to a device that is only capable of receiving audioinputs, e.g., an audio amplifier.FIGURE A2EXAMPLE RECEIVER CIRCUITSAE J2366-1L Issued NOV2001-7-A.1.3 Transceiver CircuitThe circuit shown in Figure A3 applies to a device that

34、 is capable of generating audiooutput and receiving audio input, e.g., a cellular phone.Notes:1. This switch is ON for transmit and receive. It is OFF only when the transceiver is turned off to avoid popnoise at power down.FIGURE A3EXAMPLE TRANSCEIVER CIRCUITSAE J2366-1L Issued NOV2001-8-A.1.4 Groun

35、ding ExampleFigure A4 shows an example of a grounding scheme that may help to reduce thepossibilities of noise interference, ground potential shifts, or ground loops.FIGURE A4SYSTEM GROUNDING EXAMPLESAE J2366-1L Issued NOV2001RationaleNot applicable.Relationship of SAE Standard to ISO StandardNot ap

36、plicable.ApplicationThis SAE Recommended Practice describes the Low Impedance Stereo Audio (LISA) bus,which may be used in conjunction with the Physical Layer of the IDB-C, as described in SAE J2366-1.The audio arbitration messages used to control access to the LISA bus are specified in SAE J2366-7.

37、The IDB-C is a non-proprietary virtual token passing bus, designed to allow disparate consumer, vehicle,and commercial electronic components to communicate and share information. Reference SectionSAE J2355ITS Data BusArchitecture Reference Model Information ReportSAE J2366-1ITS Data BusPhysical LayerSAE J2366-2ITS Data BusLink LayerSAE J2366-4ITS Data BusThin Transport LayerSAE J2366-7ITS Data BusApplication Message LayerSAE J2590PMODE for In-Vehicle NetworksDeveloped by the ITS Data Bus Committee