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...
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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)....
Acknowledgement and Retransmit
Specification • The receiver shall send a positive acknowledgment (ACK) packet for each DATA packet received without error.
Acronyms
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...
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...
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...
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...
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...
Analog to Digital Converter and Multiplexer
Profile • SMAC ADC and Analog MUX The SMAC shall include an ADC to take analog measurements of board parameters (voltage, current, temperature). These values are returned to the system controller as SOH information. An analog MUX may be required so that multiple analog values can be read by the ADC. The...
Applications
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...
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
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)...
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...
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...
Buckling and Crippling
Specification • Evaluation of buckling strength shall consider the combined action of primary and secondary stresses and their effects on general instability, local or panel instability, crippling, and creep.
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...
Buffer Segmentation 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 JEEP MTU size, the buffer must be segmented into a series of JEEP packets and then reassembled at the receive TEP before returning the buffer to the...
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...
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...
Channel Independence
Specification • Each transport channel shall operate independently from other transport channels.
Channel Operations
Specification •
Characteristics
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...
Cleanliness
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.
Coating Surface Resistivity
Specification • The thickness of all chemical film treatments need to be controlled to provide low surface resistivity. Surface resistivity shall be less than 1 x 109 ohm/ square.
Coating Volume Resistivity
Specification • All paints and coatings shall have a volume resistivity less than 1 x 109 ohm-cm.
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