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This document is intended to explain, in detail, the rationale behind the features and functions of the AS4074, Linear, Token-passing, Bus (LTPB). The discussions also address the considerations which a system designer should take into account when designing a system using this bus. Other information can be found in these related documents: AIR4271 - Handbook of System Data Communication AS4290 - Validation Test Plan for AS4074

This document is intended to explain, in detail, the rationale behind the features and functions of the AS4074, Linear, Token-passing, Bus (LTPB). The discussions also address the considerations which a system designer should take into account when designing a system using this bus. Other information can be found in these related documents:

This Handbook has been prepared by the Ring Implementation Task Group of the SAE AS-2 Committee, and is intended to support AS4075 by providing explanation of the standard itself and guidance on its use. The principal objective in the preparation of a standard is to provide a statement of operational and performance requirements, and an unambiguous definition of the functions to be realized in any implementation, primarily from the view point of interoperability. While efforts have been made within the AS4075 standard to provide a readable general description of the HSRB, detailed explanations, rationale and guidance to the use are incompatible with the purpose and, indeed, the format of a standard. Accordingly, this Handbook contains a paragraph-by-paragraph explanation of the main sections of the standard, and a discussion of application and implementation issues.

This Handbook has been prepared by the Ring Implementation Task Group of the SAE AS-2 Committee, and is intended to support AS4075 by providing explanation of the standard itself and guidance on its use. The principal objective in the preparation of a standard is to provide a statement of operational and performance requirements, and an unambiguous definition of the functions to be realized in any implementation, primarily from the view point of interoperability. While efforts have been made within the AS4075 standard to provide a readable general description of the HSRB, detailed explanations, rationale and guidance to the use are incompatible with the purpose and, indeed, the format of a standard. Accordingly, this Handbook contains a paragraph-by-paragraph explanation of the main sections of the standard, and a discussion of application and implementation issues.

The original purpose of this document was to establish interface requirements for modular avionics backplanes to be prototyped up to 1995. The document was issued as ARD50011 in September 1992. It is being reissued as an SAE Aerospace Information Report (AIR) in order to: a Preserve the requirements for more than 2 years b Support design of retrofits and avionics systems to be fielded in the years 1995 to 2000 c Provide a baseline for updating the requirements of future integrated systems These requirements were and are intended to promote standardization of modular avionic backplane interfaces. These requirements have been driven predominantly, but not exclusively, by aerospace type military platforms.

The original purpose of this document was to establish interface requirements for modular avionics backplanes to be prototyped up to 1995. The document was issued as ARD50011 in September 1992. It is being reissued as an SAE Aerospace Information Report (AIR) in order to: a Preserve the requirements for more than 2 years b Support design of retrofits and avionics systems to be fielded in the years 1995 to 2000 c Provide a baseline for updating the requirements of future integrated systems These requirements were and are intended to promote standardization of modular avionic backplane interfaces. These requirements have been driven predominantly, but not exclusively, by aerospace type military platforms.

This SAE Aerospace Standard (AS) has been prepared by the Ring Implementation Task Group of the SAE AS-2 Committee. It is intended as a companion document to the SAE AS4075 High Speed Ring Bus Standard. While the Standard is intended to provide as complete a description as possible of an HSRB implementation, certain parameters are system-dependent and evolutionary. This document contains those parameters. The text through Table 1 is intended to provide definitions and descriptions applicable to all applications. Table 2 contains specific parameter values for one or more implementations. This table will change as new systems are implemented or new HSRB speed options are defined.

This SAE Aerospace Standard (AS) has been prepared by the Ring Implementation Task Group of the SAE AS-2 Committee. It is intended as a companion document to the SAE AS4075 High Speed Ring Bus Standard. While the Standard is intended to provide as complete a description as possible of an HSRB implementation, certain parameters are system-dependent and evolutionary. This document contains those parameters. The text through Table 1 is intended to provide definitions and descriptions applicable to all applications. Table 2 contains specific parameter values for one or more implementations. This table will change as new systems are implemented or new HSRB speed options are defined.

MIL-STD-1553 establishes requirements for digital command/response time division multiplexing (TDM) techniques on military vehicles, especially aircraft. The existing MIL-STD-1553 network operates at a bit rate of 1 Mbps and is limited by the protocol to a maximum data payload capacity of approximately 700 kilobits per second. The limited capacity of MIL-STD-1553 buses coupled with emerging data rich applications for avionics platforms plus the expense involved with changing or adding wires to thousands of aircraft in the fleet has driven the need for expanding the data carrying capacity of the existing MIL-STD-1553 infrastructure.

MIL-STD-1553 establishes requirements for digital command/response time division multiplexing (TDM) techniques on military vehicles, especially aircraft. The existing MIL-STD-1553 network operates at a bit rate of 1 Mbps and is limited by the protocol to a maximum data payload capacity of approximately 700 kilobits per second. The limited capacity of MIL-STD-1553 buses coupled with emerging data rich applications for avionics platforms plus the expense involved with changing or adding wires to thousands of aircraft in the fleet has driven the need for expanding the data carrying capacity of the existing MIL-STD-1553 infrastructure.

This standard establishes the design requirements for a fiber optic serial interconnect protocol, topology, and media. The application target for this standard is the interconnection of multiple aerospace sensors, processing resources, bulk storage resources and communications resources onboard aerospace platforms. The standard is for subsystem interconnection, as opposed to intra-backplane connection.

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 data 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 m can be accommodated.

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 data 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 m can be accommodated.

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 data 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 m can be accommodated.

IEEE-1394b, Interface Requirements for Military and Aerospace Vehicle Applications, establishes the requirements for the use of IEEE Std 1394™-2008 as a data bus network in military and aerospace vehicles. The portion of IEEE Std 1394™-2008 standard used by AS5643 is referred to as IEEE-1394 Beta (formerly referred to as IEEE-1394b.) It defines the concept of operations and information flow on the network. As discussed in 1.4, this specification contains extensions/restrictions to “off-the-shelf” IEEE-1394 standards and assumes the reader already has a working knowledge of IEEE-1394. This document is referred to as the “base” specification, containing the generic requirements that specify data bus characteristics, data formats, and node operation.