Communication Profile

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Addressing

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...

Communication Profile > Interconnect Technologies > SpaceWire Interconnect > SpaceWire Transport > Addressing

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...

Communication Profile

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...

Communication Profile > Functional Description

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...

Communication Profile > Interconnect Technologies

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...

Communication Profile > Functional Description > JAS CCSDS SOIS

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...

Communication Profile > Interconnect Technologies > SpaceWire Interconnect > SpaceWire Logical > JAS Efficient Exchange Protocol

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,...

Communication Profile > Interconnect Technologies > SpaceWire Interconnect > SpaceWire Logical > JAS Reliable Data Delivery Protocol

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...

Communication Profile > Subnetwork Services > Memory Access Service

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...

Communication Profile > Interconnect Technologies > SpaceWire Interconnect > SpaceWire Transport > Multicast/Broadcast

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...

Communication Profile > Interconnect Technologies > SpaceWire Interconnect > SpaceWire Transport > Network Discovery

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...

Communication Profile > Subnetwork Services > Packet Service

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...

Communication Profile > Interconnect Technologies > RapidIO Interconnect

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...

Communication Profile > Interconnect Technologies > RapidIO Interconnect > RapidIO Logical

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...

Communication Profile > Interconnect Technologies > RapidIO Interconnect > RapidIO Physical

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...

Communication Profile > Interconnect Technologies > RapidIO Interconnect > RapidIO Transport

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...

Communication Profile > Interconnect Technologies > SpaceWire Interconnect > SpaceWire Logical > Remote Memory Access Protocol

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...

Communication Profile > Functional Description > SOIS Applied to JAS

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...

Communication Profile > Interconnect Technologies > SpaceWire Interconnect

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...

Communication Profile > Interconnect Technologies > SpaceWire Interconnect > SpaceWire Logical

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