Profile • SpaceWire supports three types of addressing: Path (Physical) Addressing, Logical Addressing, and Regional Addressing. JAS uses regional addressing because it provides the greatest flexibility to create scalable networks. Regional addressing uses a two-byte scheme where the first byte identifies the router and the second byte identifies the endpoint address connected...
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Communication Profile
Profile • The Communication Profile defines standard interfaces for facilitating communication between RP, CH, and PS nodes within a JAS system. The Communication Profile focuses primarily on communication between payload applications. It leverages industry standards to support network-based communication using serial interfaces. A common set of communication protocols for space applications has...
Functional Description
Profile • The Communication Profile defines standard methods for transferring data between two JAS nodes. This includes the use of protocols and packet formats by hardware and software. Applications become portable and reusable by using layered communication architecture. The applications should be agnostic to the choice of physical interconnect technology, which allows...
Interconnect Technologies
Profile • This profile describes the interconnect technologies supported by JAS. Each interconnect will be comprised of three layers based on the RapidIO standard: the Logical Layer; the Transport Layer; and the Physical Layer. The figure below shows a mapping of the interconnect layers to the OSI layers. The Application Layer is...
JAS CCSDS SOIS
Profile • The JAS communication architecture is based on the Consultative Committee for Space Data Systems (CCSDS) Spacecraft Onboard Interface Services (SOIS) reference communication architecture. SOIS describes a layered architecture that allows applications to be abstracted from the specific communication data links. The SOIS architecture describes four layers: the Application Layer, the...
JAS Efficient Exchange Protocol
Profile • The JAS Efficient Exchange Protocol (JEEP) is a best-effort packet transmission protocol that can be used to send messages between applications over a SpaceWire data link. JEEP is similar to the JRDDP protocol in that provides a segmentation capability to promote fairness between all applications needing to communicate on the...
JAS Packet Protocol
Profile • The JAS Packet Protocol (JPP) provides the capability to send a single JAS Packet over a SpaceWire data link. JPP is just an encapsulation of a JAS Packet within a SpaceWire packet. Even though it is classified as a SpaceWire protocol, there are no QoS functions provided apart from those...
JAS Reliable Data Delivery Protocol
Profile • The JAS Reliable Data Delivery Protocol (JRDDP) is a reliable packet transmission protocol that can be used to send messages between applications over a SpaceWire data link. It is based on a protocol created by the National Aeronautics and Space Administration (NASA) at the Goddard Spaceflight Center in Greenbelt, Maryland,...
Memory Access Service
Profile • The Memory Access Service is used to asynchronously read and write to memory-based devices across a network. The Memory Access Service is based on the CCSDS SOIS Memory Access Service and provides a layer of abstraction between applications and memory-based devices. It provides a common API for applications to use...
Multicast/Broadcast
Profile • SpaceWire doesn’t inherently support a multicast or broadcast capability. There is a time-code distribution function but it is limited in the amount of user information that can be distributed. An approach has been developed for a broadcast capability through custom router and endpoint modifications. It uses a set of dedicated...
Network Discovery
Profile • When probing for routing switches, early network discovery techniques typically relied on each routing switch’s configuration port to respond to identification requests to confirm the routing switch’s presence. A request packet was typically dispatched to the configuration port, and a response packet provided confirmation of existence. This same request/response approach...
Networks
Profile • Each JAS node should contain a SpaceWire Router per the SMAC Profile which allows for extensive scaling of the network. A network is made up of a number of links, nodes (endpoints) and routing switches. Links provide the means for passing packets from one node to another. Nodes can be...
Packet Service
Profile • A packet service is used to send messages between applications. JAS assumes that each processing element has one packet service for each packet format that is defined. In order to promote reuse, a layered architecture is used whereby applications are abstracted from the packet format details. The packet service contains...
Packets
Profile • The basic form of a SpaceWire packet is shown below. More details about SpaceWire packets can be found in the Communication Specification. The format contains the following: One or more 8-bit addresses that allow the packet to be routed through the network An 8-bit protocol identifier which allows multiple protocols...
RapidIO Interconnect
Profile • RapidIO technology is a packetized point-to-point interconnect fabric. Packets carry user-definable payloads from 1 to 256 bytes. Both serial and parallel physical interfaces are defined, allowing effective data rates from 667 Mbps to 30 Gbps. The serial version of RapidIO was chosen for JAS because it requires a small number...
RapidIO Logical
Profile • The Logical Layer specifications define the operations and associated transactions by which end point processing elements communicate with each other. It is composed of several specifications, each providing packet formats and protocols for different transaction semantics. The Logical I/O specification defines packet formats for read, write, write-with-response, and various atomic...
RapidIO Physical
Profile • The Physical Layer defines how adjacent processing elements electrically connect to each other. The physical layer specifications describe the electrical requirements for connecting endpoints and switches together. The Parallel Physical specification was deprecated in 10/2013 and is no longer used. The Serial Physical specification outlines the requirement for devices utilizing...
RapidIO Transport
Profile • The Transport Layer defines how transactions are routed from one end point processing element to another through switch processing elements. The Transport specification describes the header information added to a RapidiIO packet and the way the header information is interpreted by a switching fabric. Every RapidIO endpoint is uniquely identified...
Remote Memory Access Protocol
Profile • RMAP is used to access memory devices across a SpaceWire data link. RMAP can be used to support many functions within a JAS-based system, such as: Configure SpaceWire routers Load and control FPGA applications Configure and control sensors Gather state of health information Initializing and retrieving the contents of memory...
Routing
Profile • SpaceWire uses wormhole routing to route packets through the network. Each packet contains a header which holds the destination node address either as the route through the network or as the identity of the destination node. As soon as the header for a packet is received the switch determines the...
SOIS Applied to JAS
Profile • A simplified version of the SOIS architecture as applied to JAS is shown in the figure below. The subnetwork services are used by applications to encapsulate and describe the data that needs to be communicated regardless of the underlying physical layer. The subnetwork services are JAS-specific implementations of the respective...
SpaceWire Interconnect
Profile • SpaceWire is a communication network designed to connect sensors, processing units, memory devices and telemetry/telecommand subsystems together within a spacecraft. It provides moderate-rate (2 to 200 Mbps), bi-directional, full-duplex, data links. Application, control, and time information is sent along a SpaceWire link in discrete packets. A SpaceWire network is comprised...
SpaceWire Logical
Profile • The SpaceWire standard defines packets and protocol identifiers. The SpaceWire Logical Layer has the flexibility to utilize standard or customized protocols. There are two classes of protocols available to JAS applications: Memory access protocols – access and control memory devices that are located on remote nodes within a network Messaging...
SpaceWire Physical
Profile • JAS based systems will follow the SpaceWire standard for the physical characteristics. The details of the JAS-based implementation of the SpaceWire physical layer are found in the Electrical Specification.
SpaceWire Transport
Profile • The Transport Layer routes messages from one end-point processing element to another through switch processing elements. The following sections describe the various elements that define the SpaceWire Transport Layer.
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