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2 D Meshes and 2 D Toroids

Other • 2-D meshes are one of the easiest topologies to visualize – nodes are connected in a “grid” fashion (see Figure). The simple layout also allows many problems to map easily to the structure of this network. 2-D Mesh and 2-D Toroid 2-D meshes have unequal node degree. The node degree...

Joint Architecture Standard Overview > Network Topologies > 2 D Meshes and 2 D Toroids

3 D Meshes and 3 D Toroids

Other • 3-D meshes and 3-D toroids are similar to 2-D meshes and toroids, except the 3-D mesh/toroid is expanded along the Z-axis to provide another dimensional layer of nodes. In the case of the 3-D toroid, the topmost nodes (along the new Z-axis) are connected to the bottommost nodes (see Figure)....

Joint Architecture Standard Overview > Network Topologies > 3 D Meshes and 3 D Toroids


Other • Acronym Definition A/D Analog-to-Digital (as in A/D converter) ACK Acknowledge ADC Analog-to-Digital Converter API Application Program Interface APID Application Identifier APP Application CCC Cube-Connected Cycles CCITT From French: Comité Consultatif International Téléphonique et Télégraphique International Telegraph and Telephone Consultative Committee CC-NUMA Cache Coherent-Non-Uniform Memory Access CCSDS Consultative Committee for Space...

Joint Architecture Standard Overview > Acronyms


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

Advantages of JAS

Other • A modern node-based architecture with reconfigurable node electronics and serial data links between nodes provides the core structure and flexibility needed to enable most of the design strategies. It offers a powerful, yet efficient, modular solution that can be scaled and configured to support payloads of virtually any size and...

Joint Architecture Standard Overview > JAS Rationale and Motivation > Advantages of JAS

Allocation of Service Types and Subtypes

Specification • The PUS provides a standard set of services that are targeted for communication between spacecraft and ground systems. Many of them may not be applicable to on-board communication between applications. However, nothing precludes their use in a JAS-based system. The PUS can be extended to add additional functionality to existing...

Communication Specification > JAS Packets > Packet Service Definitions > Allocation of Service Types and Subtypes

Analog Electronics

Profile • This instantiation of the Expansion Profile implements a 6U VPX board to include analog electronics and connectors to access incoming signals from external sensor modules. The analog electronics are connected to an RP node through the system backplane. The FPGA on the RP node filters and processes the incoming data...

Expansion Profile > Applications > Analog Electronics


Profile • Common instantiations of the CH profile include, but are not limited to: Host Vehicle Interface and Configuration Manager Mission Data Processing Non-Volatile Memory Storage Mass Memory Node The CH node can operate in several capacities, the most essential of which is the Host Vehicle Interface and Configuration Manager. However, several...

Command and Host Processor Profile > Applications


Profile • Instantiations of the Expansion Profile can improve the versatility of other node profiles by adding additional capability, connectivity, or capacity. Common instantiations of the Expansion Profile include, but are not limited to: Host vehicle interface Memory storage Rear transition module Analog electronics

Expansion Profile > Applications


Profile • Instantiations of this profile are intended to function as primary-to-secondary power converters, producing the secondary voltage rail(s) that are distributed to other nodes. The ‘Local POL Power Conversion’ section mentions one “or more secondary voltage rails” being produced by the PS node. One voltage rail (typically +5 or +12 V)...

Power Supply Profile > Applications

Backplane Connectors

Specification • JAS electrical design should utilize commercial connector standards when applicable. The VPX plug-in module to backplane connector is a Tyco Electronics MultiGig RT2 connector system which was chosen for its rugged mechanical performance and high-speed electrical performance, rated to 6.4 Gb/s and demonstrated to support data rates greater than 10...

Electrical Specification > Electrical Interconnects > VPX > Backplane Connectors

Backplane Topology

Specification • The backplane is a key element in achieving high-speed connections between the plug-in modules or nodes in the case of a JAS system. VPX compliant backplanes support a minimum signaling rate of at least 3.125 Gbps on any differential point-to-point connection. There are a small number of required signals on...

Electrical Specification > Electrical Interconnects > VPX > Backplane Topology

Buffer Fragmentation and Reassembly

Specification • In cases where a higher-level transmit application (or higher layer in a communications stack) must transmit a buffer of data that exceeds the JRDDP MTU size, the buffer must be fragmented into a series of JRDDP packets and then reassembled at the receive TEP before returning the buffer to the...

Communication Specification > SpaceWire > Protocols > JAS Reliable Data Delivery Protocol > Overall Functional Description > Buffer Fragmentation and Reassembly

CCSDS Telecommand and Telemetry Format Packet Standard

Specification • CCSDS Space Packet The CCSDS packet format consists of a packet primary header and packet data field. The header provides routing information for the packet and metadata that describes the packet. The data field is intended to be a user-defined field that can be customized for applications. Details of how...

Communication Specification > JAS Packets > CCSDS Telecommand and Telemetry Format Packet Standard

Channel Closing Process

Specification • The following sections present the interactions (in the form of UML Sequence Diagrams) between transmit and receive endpoints while closing a channel. Various error conditions are presented in order to show nominal, delayed, and worst case scenarios. The hexagonal icons represent the TEP states while the dashed green lines represent...

Communication Specification > SpaceWire > Protocols > JAS Reliable Data Delivery Protocol > Channel Operations > Channel Closing Process


Other • The table below describes the characteristics of JAS. Characteristic Definition Modularity Modular, scalable design capable of accommodating a wide range of applications, complexities and performance needs Configurable Topology Flexible, node-based, topologically configurable architecture that can be easily sized, configured and optimized to meet connectivity and robustness needs of a broad...

Joint Architecture Standard Overview > JAS Rationale and Motivation > Characteristics


Specification • Cleanliness is an important design consideration which can be mitigated by the mechanical structure and processes. Systems adjacent to an optical payload may have more strict cleanliness requirements than non-optical payload. The following sections describe the requirements which deal with Cleanliness considerations for the JAS mechanical structure.

Mechanical Specification > Design Constraints > Cleanliness

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