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1、AEROSPACE STANDARD Issued 1993-12 AS4074 Linear Token Passing Multiplex Data Bus TABLE OF CONTENTS 1.SCOPE 3 2.REFERENCES. 3 2.1Applicable Documents.3 2.1.1SAE Publications 3 2.1.2Military Publications.4 2.2Acronyms and Abbreviations 4 3.GENERAL REQUIREMENTS7 3.1General Description.7 3.1.1Media Acce
2、ss. 9 3.1.2Low Latency for High Priority Messages 10 3.1.3Station Failures 10 3.1.4Logical Ring Admittance.10 3.1.5Logical Ring Initialization 10 3.1.6System Monitor 11 3.2Media Interface Unit (MIU). 11 3.2.1Symbol Set. 11 3.2.2Transmitter, Receiver, and Media Characteristics13 3.2.3Media Redundancy
3、 Requirements. 24 3.2.4Transmission Monitoring 25 3.3Media Access Protocol Facilities 26 3.3.1Frame Formats.26 NONCURRENT NOTICE This specification has been declared “NONCURRENT“ as of October 2004. It is recommended, therefore, that this document not be specified for new designs. Each of these “NON
4、CURRENT“ documents is available from SAE. 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 entirely voluntary, and its applicability and suitability for any particular use, includi
5、ng any patent infringement arising therefrom, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions. Copyright 2004 SAE International All rights
6、 reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER:Tel: 877-606-7323 (inside USA and
7、Canada) Tel: 724-776-4970 (outside USA) Fax: 724-776-0790 Email: custsvcsae.org SAE WEB ADDRESS:http:/www.sae.org Noncurrent 2004-10 Superseding AS4074 REV. A SAE AS4074 Revision A - 2 - TABLE OF CONTENTS (Continued) 3.4.3Test Messages. 51 3.4.4BIU Initialization. 54 3.4.5Built-In-Test Functions. 54
8、 3.4.6Time Synchronization Report. 56 4.LINEAR TOKEN PASSING MULTIPLEX DATA BUS TESTING58 4.1Test Plan 58 4.2Test Management 58 5.TPIU STATE MACHINE DEFINITION58 5.1Idle State (S0) 59 5.2Claim Token State (S1) 61 5.3Check Token Address State (S2). 63 5.4Send Message State (S3) 63 5.5Pass Token State
9、 (S4). 64 5.6Check Token Pass State (S5) 64 5.7Check Message Address State (S6) 65 5.8Receive Message State (S7)65 APPENDIX ATRANSMISSION MEDIA SLASH SHEETS. 66 FIGURE 3.1-1Linear Token Passing Bus Block Diagram. 8 FIGURE 3.1-2Logical Ring Superimposed on a Linear Bus.9 FIGURE 3.2.1.2-1Overall Frame
10、 Structure. 12 FIGURE 3.2.2.1.2.4-1 Fiber Optic Transmitter Output Waveform. 15 FIGURE 3.2.2.1.3.2-1 Transmitter/Receiver Optical Power Levels. 17 FIGURE 3.2.2.1.3.4-1 Fiber Optic Receiver Input Waveform 18 FIGURE 3.2.2.2.2.3-1 Electrical Transmitter Output Waveform 22 FIGURE 3.2.2.2.3.1-1 Electrica
11、l Receiver Input Waveform. 23 FIGURE 3.3.1-1Token Passing Protocol Frame Formats. 27 FIGURE 3.3.1-2Frame Control Field Definitions. 28 FIGURE 3.3.2-1Send Message State Flowchart 31 FIGURE 3.4.1-1Mode Control Command Format. 35 FIGURE 3.4.1.1-1BIU Command Register Format 36 FIGURE 3.4.1.2-1BIU Comman
12、ded Modes. 37 FIGURE 3.4.2-1Load/Report Configuration Command Format 42 FIGURE 3.4.2.1-1Configuration Report Format 45 FIGURE 3.4.2.2-1Status Report Format.48 FIGURE 3.4.2.2.1-1BIU Status Register Format 49 FIGURE 3.4.2.2.2-1BIU Error Register Format 50 FIGURE 3.4.2.3-1Time Report Format 52 FIGURE 3
13、.4.3-1Test Message Format. 53 FIGURE 3.4.6.1-1Time Synchronization Message Format 57 FIGURE 5-1TPIU State Diagram 60 TABLE 5-1State Transition Table. 61 3.3.2Timers 30 3.3.3Traffic Summary. 34 3.4Station Management 34 3.4.1Mode Control Command 35 3.4.2Load/Report Configuration. 41 -,-,- - 3 - 1.SCOP
14、E: This standard specifies the characteristics of the SAE Linear Token Passing Bus (LTPB) Interface Unit. The LTPB provides a high reliability, high bandwidth, low latency serial interconnection network suitable for utilization in real time military and commercial applications. Multiple redundant da
15、ta paths can be implemented to enhance reliability and survivability in those applications which require these attributes. The token passing and data exchange protocols are optimized to provide low latency and fast failure detection and correction. Physical configurations with bus lengths up to 1000
16、 m can be accommodated. This specification defines the following: a.General Description (3.1):An overview of the LTPB protocol. b.Physical Media Interface (3.2):This portion of the standard defines the physical interface to both optical and electrical bus media. c.Access Protocol Definition (3.3):Th
17、is portion of the standard defines the symbols, frame formats, timing functions and traffic recording requirements of the Token Passing Interface Unit (TPIU). d.Network Protocol Definition (3.4):This portion of the standard defines the network control and station management functions. e.Test and Ver
18、ification (Section 4):This paragraph defines the responsibilities and methods for test and verification of the LTPB. f. TPIU State Machine (Section 5):This section defines the TPIU States and state transition rules. 2.REFERENCES: 2.1Applicable Documents: The following publications form a part of thi
19、s specification to the extent specified herein. The latest issue of all SAE Technical Reports shall apply. 2.1.1SAE Publications:Available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001. AIR4288Linear Token Passing Multiplex Data Bus Users Handbook AS4290DRAFT Validation Test Plan for A
20、S4074 linear Token Passing Multiplex Data Bus SAE AS4074 Revision A -,-,- - 4 - 2.1.2Military Publications:Available from DODSSP, Subscription Services Desk, Building 4D, 700 Robbins Avenue, Philadelphia, PA 19111-5094. 2.2Acronyms and Abbreviations: Amax Maximum end-to-end attenuation AminMinimum e
21、nd-to-end attenuation Ar Attenuation of reflected signals bps Bits per second BAT Bus Activity Timer BIT Built-In-Test BIU Bus Interface Unit BTO BAT Timeout BW Spectral Bandwidth CRCCyclic Redundancy Check C/B Center of Bit CTLC Claim Token Limit Counter dB Decibel dBm Decibel referenced to 1 milli
22、watt Dclad Fiber Optic cladding diameter Dcm Maximum total dispersion Dcore Fiber Optic core diameter Dgp Group propagation delay difference Dj Jitter DA Destination Address field (may contain physical or logical address depending on frame type) exp Exponential value (raised to the power) ED End Del
23、imiter ELRX Electrical Receiver ELTX Electrical Transmitter ERA Bus A Error ERB Bus B Error E/T End of Transmission F Frequency FC Frame Control FORX Fiber Optic Receiver FOTX Fiber Optic Transmitter FT Frame Type FW Filter Word GCD Global Clock Differential ISO/DIS 7498 22 April 1982 International
24、Systems Organization Open Systems Interconnection - Basic Reference Model, Draft International Standard N1406 March 1983 Working Draft for an Addendum to ISO 7498 Covering Connectionless Data Transmission SAE AS4074 Revision A -,-,- - 5 - 2.2(Continued): HEX Hexadecimal INFO Information Field JIAWG
25、Joint Integrated Avionic Working Group KHz Kilohertz LC Load Configuration LLC Logical Link Control LTPB Linear Token Passing Bus m Bit position in FW field M Optical Margin MAC Media Access Control Mbaud Megabaud Mbps Megabits per Second MER Message Error MFCS Message Frame Check Sequence MHz Megah
26、ertz MIU Media Interface Unit MPDU Message Protocol Data Unit MSA Maximum Station Address in logical ring Nct Number of words in Claim Token Frame NA Numerical Aperture NSA Next Station Address in logical ring P Preamble Pr Receiver Minimum Valid Preamble Length Pt Transmitter Preamble Length Px Pri
27、ority PDU TPIU Protocol Data Unit PSA Physical Station Address Rber Receiver Bit Error Rate Rcmr Receiver Common Mode Rejection Ratio Rd Data Rate (Mbps) Rf Receiver Maximum Fall Time (90% to 10%) Ridr Receiver Intertransmission Dynamic Range Riz Receiver Input Impedance Rnv Receiver Noise Voltage I
28、nput Ror Receiver Operating Range Rous Receiver Combined Over/Undershoot Rp Receiver Optical Power Input Rpwd Receiver Input Maximum Pulse Width Distortion Rpm Receiver Minimum Optical Power Input Rpo Receiver Maximum Optical Power Input Rr Receiver Maximum Rise Time (10% to 90%) Rs Signaling Rate S
29、AE AS4074 Revision A -,-,- - 6 - 2.2(Continued): Rtm Start-of-Bit to Center-of-Bit Rto Start-of-Bit to Start-of-Bit Rvm Receiver Minimum Input Voltage Rvo Receiver Maximum Input Voltage Rx Receiver RAT Ring Admittance Timer RC Report Configuration RQF Receive Queue Full RS Report Status RT Report Ti
30、me RMT Redundant Media Timeout RMS Redundant Media Skew Error RMS Root Mean Square RPB Receiver Primary Bus RPE Receiver Parity Error RXE Receiver Enable RXM Receive Message Available Sd Surge Voltage Duration Sitg System Minimum Intertransmission Gap Sv Surge Voltage S0 Idle State S1 Claim Token St
31、ate S2 Check Token Address State S3 Send Message State S4 Pass Token State S5 Check Token Pass State S6 Check Message Address State S7 Receive Message State SA Source Address SD Start Delimiter S/B Start-of-Bit S/T Start-of-Transmission SMC Station Management Code Tba Bus Activity Indication Time Td
32、 Clock Maximum Uncompensated Drift Rate Tpwd Transmitter Maximum Pulse Width Distortion Tds Data Streaming Timer Tf Transmitter Maximum Fall Time (90% to 10%) Tiz Transmitter Drive Impedance Tm Minimum Duration between Transitions Tms Master and Most Distant Slave Station (Global Timer) To Nominal B
33、it Time Tous Transmitter Combined Over/Undershoot Tpd Propagation Delay Time Tpl Transmitter Optical Leakage Power Tpo Transmitter Optical Power Tpr Transmitter Residue Power Tr Transmitter Maximum Rise Time (10% to 90%) SAE AS4074 Revision A -,-,- - 7 - 2.2(Continued): Tsk Transmitter Redundant Med
34、ia Skew Time Tsr Maximum Station Response Time Ttm Transmitter Minimum Signaling Duration Tto Transmitter Nominal Bit Time Ttp Token Passing Time Value Tu Time Master Update Rate (milliseconds) Tvo Transmitter Output Voltage Level Tvr Transmitter Peak Output Voltage Tx Transmitter TBD To Be Determin
35、ed TFCS Token Frame Check Sequence THT Token Holding Timer TIME Global Clock Value (48 bits) TPIU Token Passing Interface Unit TMA Transmit Message Aborted TMD Time Master Disable TME Time Master Enable TPE Transmitter Parity Error TPT Token Passing Timer TRT Token Rotation Timer TRTx Token Rotation
36、 Timer (for priority level “x“) TS This Station TSM Time Synchronization Message TTA Bus A Transmission Monitor Timeout TTB Bus B Transmission Monitor Timeout TTO TPT Timeout TXE Transmitter Enable TXM Transmit Message W1 Optical Wavelength Lower W2 Optical Wavelength Upper WC Word Count WCE Message
37、 Word Count Error 3.GENERAL REQUIREMENTS: 3.1General Description: The LTPB shall consist of a set of stations connected by a broadcast transmission medium - that is, each station which transmits shall be heard by all of the other stations. Stations shall accept a transmission based upon either physi
38、cal or logical addressing mechanisms. The functional block diagram for the LTPB is shown in Figure 3.1-1 along with its relationship to the ISO OSI Basic Reference Model. It shall consist of the following elements: a.Physical Media:The Physical Media shall be composed of 1 or 2 physical bus paths. E
39、ach bus path shall be characterized as a broadcast medium. SAE AS4074 Revision A -,-,- - 8 - SAE AS4074 Revision A -,-,- - 9 - 3.1(Continued): b.Bus Interface Unit (BIU):The BIU interfaces to the bus media and the Host. Each bus path shall be an independent entity requiring a Media Interface Unit (M
40、IU). One TPIU shall serve all implemented MIUs. The remainder of the BIU shall perform station management, network management, and Host interface functions. 3.1.1Media Access:Access to the media shall be controlled by the Token. The Token is continually passed around a logical ring (see Figure 3.1-2
41、) superimposed on the linear bus. A station receiving the Token gains the right to make a transmission on the medium for a certain amount of time. This amount of time depends upon the following quantities: a.Value of the Token Holding Timer (THT), used for all messages of priority 0, as well as; b.T
42、he residual value of the Token Rotation Timers (TRTs), one for each priority from 1 to 3. This amount of time shall always be less than or equal to a predetermined maximum value. When this amount of time has expired, or the station has sent all of its messages, then the station shall forward the Tok
43、en to the next member of the logical ring. SAE AS4074 Revision A -,-,- - 10 - 3.1.2Low Latency for High Priority Messages:Low latency for high priority messages shall be assured by the use of message priority TRTs. A station which has a message at the highest priority (Priority 0) shall always send
44、that message when it receives the Token. Priority 0 messages continue to be sent until there are no Priority 0 messages or the THT expires. If that station has lower priority messages to send, it will send those messages as long as the TRT associated with that priority level has not expired. Otherwi
45、se, the station must forward the Token to its successor. In this way the token passing bus users shall defer to higher priority traffic when the traffic load becomes heavy. 3.1.3Station Failures:Station failures shall be handled by the station immediately preceding the failed station in the logical
46、ring sequence. The station passing the Token shall verify that there is Bus Activity. After two consecutive attempts at passing the Token the station shall automatically increment the destination address in the Token and try again. This incremental bridging shall continue until the station finds a s
47、uccessor or the destination address wraps around and matches the local station address, at which time the station shall cease its attempts to find a successor. 3.1.4Logical Ring Admittance:Stations shall be allowed admittance to the logical ring on a periodic basis. Each station shall contain a Ring Admittance Timer (RAT). When this timer expires and there is a gap between the local stations address and that of its successor then the Token shall be passed to the sequential address following that of the local station. The normal
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