Standard

SAE AS5643B

Published

Note: This standard has a new edition: SAE AS5643B

Singles purchase not accessible

This standard can not be purchased as a single sales.

Abstract

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. It is important to note that this specification is not designed to be standalone; several requirements leave the details to the implementations and delegate the actual implementation to be specified by the network architect/integrator for a particular vehicle application. This information is typically contained in a “network profile” slash sheet that is compliant with this base specification. In a similar manner, the electrical characteristics of the bus media, as well as connector information, is contained in a “physical layer” slash sheet that also may be unique to a particular vehicle application.  In summary, full understanding of this specification requires knowledge of IEEE Std 1394™-2008 standards and access to the physical layer slash sheets, slash sheets, and handbook for the target application. Purpose  The purpose of this document is to standardize an approach to using IEEE-1394 in safety-critical/mission-critical applications for military and aerospace vehicles. The information herein will be used to assist the design, fabrication, and maintenance of the nodes that interface via the vehicle’s network.  This document is controlled and maintained by SAE International with technical support from Remote Node vendors. Application  The IEEE-1394 Network defined in this document provides a deterministic, rate-based communication protocol overlaid on the existing IEEE-1394 standard capabilities.  Interpretation  The following interpretations shall be placed upon these words, unless stated otherwise, where they are used in this document.  May: An allowed action.  Shall: A mandatory requirement.  Should: A recommended action.  Will: A declaration of intent. Additions to the IEEE Std 1394™-2008  Standard Additions include the use of asynchronous stream packets, a fixed frame rate synchronized with a Start Of Frame packet, addition of a Vertical Parity Check, static assignment of channel numbers, pre-assignment of bandwidth, and use of Anonymous Subscriber Messaging. IEEE Std 1394™-2008 was baselined using IEEE-1394-1995 and amendments: IEEE Std 1394a-2000; IEEE Std 1394b-2002, and IEEE Std 1394c-2006.  Use of Asynchronous Streams  Asynchronous streams are used for the majority of communication on the network. Asynchronous and isochronous packets are not required but may be utilized. Architectures and protocols discussed in the context of this document are based on asynchronous streams, unless otherwise mentioned. An example of using asynchronous packets would be to allow test equipment to read data from a Configuration ROM. An example of using isochronous packets would be for streaming video and/or audio. A Fixed Frame Rate  If isochronous packets are not utilized, there is no requirement for Cycle Start packets to be sent at the normal 125-µs rate. Instead, this implementation provides a fixed frame rate for synchronization of the network. If isochronous packets are utilized, it is necessary to utilize the Cycle Master function so the 125-µs periodic cycle starts are available to isochronous sources that expect them. Figure 20 in 3.3.3.3 shows an example of interleaving isochronous packets and asynchronous stream packets.  Synchronization via Start of Frame Packets  A Start Of Frame (STOF) packet is transmitted by the Control Computer on each bus at a periodic (e.g., 100 Hz) frame rate. This packet informs all nodes on the bus that a new frame has started.  Static Assignment of Channel Numbers  Asynchronous stream packets use the same packet format as isochronous packets; therefore, the destination of the packet is identified by a channel number. Unlike commercial applications, channel numbers are not allocated through the Isochronous Resource Manager (IRM). Instead, the channel numbers for each node on the bus are pre-assigned, are application specific, and will be defined as required by the architecture.  Pre-Assignment of Bandwidth  Unlike commercial applications, the static nature of AS5643 implementations allow bandwidth to be pre-assigned. Transmit and receive times for each node on the bus are assigned as offsets, in increments of 1 µs, from the start of each frame (STOF packet). The offsets for each node on the bus are application specific and will be defined as required by the architecture.  Vertical Parity Check  Vertical Parity Checking (VPC) is performed on the data area of each packet as an adjunct to the Cyclic Redundancy Check (CRC) performed by the 1394 physical layer devices. The VPC provides additional data integrity as the messages progress through the physical and software layers.  Anonymous Subscriber Messaging  Anonymous Subscriber Messaging (ASM) is a protocol in which a Remote Node on the network can subscribe to each message that it requires. The ASM software in the Remote Node will forward only the messages to which the Remote Node has subscribed.  ASM is an upper level protocol tailored for the demands of highly modular embedded real-time systems operating under a “data push” paradigm. ASM is designed to be independent of lower level protocols and, as such, does not utilize the 1394 header to transport ASM-peculiar information. ASM is tailored to support deterministic, secure, low-latency communication between processors, sensors, instrumentation, and displays in mission-critical applications. It uses Message IDs to decouple the network traffic from physical addresses so application software can communicate without knowledge of network topology.

Document information

  • Standard from SAE_AC
  • Published:
  • Version: 0
  • Document type: IS