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This section defines the scope of the document, provides a brief history of the Pi-Bus, discusses key features of the Pi-Bus, and provides an overview of the operation of the Pi-Bus. This document is a handbook intended to accompany AS4710 Pi-Bus standard. The purpose of this document is to provide information to aid users of the Pi-Bus, whether they be implementors of Pi-Bus controllers, architects of systems considering using the Pi-Bus, or programmers who must develop applications in a system which uses the Pi-Bus as the backplane communications bus. This document also provides rationale for many of the Pi-Bus requirements as defined in AS4710 and a discussion of potential enhancements that are being considered for the Pi-Bus.

This section defines the scope of the document, provides a brief history of the Pi-Bus, discusses key features of the Pi-Bus, and provides an overview of the operation of the Pi-Bus. This document is a handbook intended to accompany AS4710 Pi-Bus standard. The purpose of this document is to provide information to aid users of the Pi-Bus, whether they be implementors of Pi-Bus controllers, architects of systems considering using the Pi-Bus, or programmers who must develop applications in a system which uses the Pi-Bus as the backplane communications bus. This document also provides rationale for many of the Pi-Bus requirements as defined in AS4710 and a discussion of potential enhancements that are being considered for the Pi-Bus.

This document contains guidance for using SAE publications, AS4112 through AS4117 (MIL-STD-1553 related Test Plans). Included herein are the referenced test plan paragraphs numbers and titles, the purpose of the test, the associated MIL-STD-1553 paragraph, commentary concerning test methods and rationale, and instrumentation requirements.

The emphasis in this standard is the development of data word and message formats for AS15531 or MIL-STD-1553 data bus applications. This standard is intended as a guide for the designer to identify standard data words and messages for use in avionics systems and subsystems. These standard words and messages, as well as the documentation format for interface control document (ICD) sheets, provide the basis for defining 15531/1553 systems. Also provided in this standard is the method for developing additional data word formats and messages that may be required by a particular system but are not covered by the formats provided herein. It is essential that any new word formats or message formats that are developed for a 15531/1553 application follow the fundamental guidelines established in this standard in order to ease future standardization of these words and messages. The standard word formats presented represent a composite result of studies conducted by the U.S.

The emphasis in this standard is the development of data word and message formats for AS15531 or MIL-STD-1553 data bus applications. This standard is intended as a guide for the designer to identify standard data words and messages for use in avionics systems and subsystems. These standard words and messages, as well as the documentation format for interface control document (ICD) sheets, provide the basis for defining 15531/1553 systems. Also provided in this standard is the method for developing additional data word formats and messages that may be required by a particular system but are not covered by the formats provided herein. It is essential that any new word formats or message formats that are developed for a 15531/1553 application follow the fundamental guidelines established in this standard in order to ease future standardization of these words and messages. The standard word formats presented represent a composite result of studies conducted by the U.S.

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.

Today's sophisticated aircraft are required to effectively perform a variety of missions. With the advent of micro-miniaturization in electronics and advanced digital computers, a new generation of avionics equipment and systems can be utilized to increase the capabilities of the aircraft. As the quantity and variety of equipment and functions increases, the problems of inter-connecting these equipments with wires presents a constraint on size, weight, signal conditioning, reliability, maintainability and electromagnetic control. Conventional wiring has resulted in large bundles of wires and many connectors which adds excessive weight and reduces the space available for the pilot and other vital elements. This limitation can be relieved significantly by the application of well proven multiplexing techniques.

The purpose of this Aerospace Recommended Practice (ARP) is to provide recommendations on the use of four types of discrete signal interfaces for unidirectional, low power, low frequency transmission of discrete information.

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 SAE Aerospace Standard (AS) contains requirements for a digital time division command/response multiplex data bus, for use in systems integration, that is functionally equivalent to MIL-STD-1553B with Notice 2. Even with the use of this document, differences may exist between multiplex data buses in different system applications due to particular application requirements and the options allowed in this document. The system designer must recognize this fact and design the multiplex bus controller (BC) hardware and software to accommodate such differences. These designer selected options must exist to allow the necessary flexibility in the design of specific multiplex systems in order to provide for the control mechanism, architectural redundancy, degradation concept, and traffic patterns peculiar to the specific application requirements.

This SAE Aerospace Standard (AS) contains requirements for a digital time division command/response multiplex data bus, for use in systems integration, that is functionally equivalent to MIL-STD-1553B with Notice 2. Even with the use of this document, differences may exist between multiplex data buses in different system applications due to particular application requirements and the options allowed in this document. The system designer must recognize this fact and design the multiplex bus controller (BC) hardware and software to accommodate such differences. These designer selected options must exist to allow the necessary flexibility in the design of specific multiplex systems in order to provide for the control mechanism, architectural redundancy, degradation concept, and traffic patterns peculiar to the specific application requirements.

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 slash sheet specifies the operational parameters and characteristics of a particular implementation of the SAE Linear, Token Passing Bus (LTPB) Interface Unit. This slash sheet defines the following: a The physical media interface: This slash sheet specifies the characteristics of the optical interface to the physical bus media. b The minimum and maximum timing requirements for operation of this implementation of the LTPB. c The data coding used to encode and decode the data for transmission. d The default values to be loaded into the timers of the LTPB interface at power-up prior to intervention by the host processor.

This slash sheet specifies the operational parameters and characteristics of a particular implementation of the SAE Linear, Token Passing Bus (LTPB) Interface Unit. This slash sheet defines the following: a The physical media interface: This slash sheet specifies the characteristics of the optical interface to the physical bus media. b The minimum and maximum timing requirements for operation of this implementation of the LTPB. c The data coding used to encode and decode the data for transmission. d The default values to be loaded into the timers of the LTPB interface at power-up prior to intervention by the host processor.

This slash sheet specifies the operational parameters and characteristics of a particular implementation of the SAE Linear, Token Passing Bus (LTPB) Interface Unit. This slash sheet defines the following: a The physical media interface: This slash sheet specifies the characteristics of the optical interface to the physical bus media. b The minimum and maximum timing requirements for operation of this implementation of the LTPB. c The data coding used to encode and decode the data for transmission. d The default values to be loaded into the timers of the LTPB interface at power-up prior to intervention by the host processor.

This slash sheet specifies the operational parameters and characteristics of a particular implementation of the SAE Linear, Token Passing Bus (LTPB) Interface Unit. This slash sheet defines the following: a The physical media interface: This slash sheet specifies the characteristics of the optical interface to the physical bus media. b The minimum and maximum timing requirements for operation of this implementation of the LTPB. c The data coding used to encode and decode the data for transmission. d The default values to be loaded into the timers of the LTPB interface at power-up prior to intervention by the host processor.