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...
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JAS Packet Service
Specification • Error: unable to migrate element with tag="" The CCSDS/SOIS subnetwork packet service standard can be referenced if a generic packet service is needed. The JAS Packet Service is an implementation of the CCSDS/SOIS packet service, specifically tailored for the JAS packet. The following diagram shows how the JAS Packet Service...
JAS Packets
Specification • Applications require a messaging format to allow them to communicate with each other. Legacy programs may already have a messaging format that they prefer to use. There is nothing that precludes any of the JAS communication protocols or data links from supporting these formats. The JAS Packet was developed for...
JAS Profile Introductions
Other • The JAS architecture defines a small number of Profiles that form the basis for building the components required for a sensor interface and data processing electronics system. A node inherits the attributes of one or more Profiles. A Profile describes the purpose of that node within the Architecture and defines...
JAS Rationale and Motivation
Other • JAS is a versatile, scalable, tailorable, SWAP-efficient, node-based concept for implementing embedded systems. Such systems include sensor suites, host platform interfaces, signal and data processors, data buffering and storage, command and data handling, and other supporting hardware and software. JAS Origin Sandia National Laboratories, Los Alamos National Laboratories, and others...
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,...
JAS Reliable Data Delivery Protocol
Specification • The JAS Reliable Data Delivery Protocol (JRDDP) uses the lower level SpaceWire data link layer to provide reliable packet delivery services to one or more higher level host application processes. This document specifies the functional requirements for JRDDP but does not specify the interfaces to the lower or higher level...
JAS Specific Services Definitions
Specification • The JAS specific services will be based on the PUS service concept. Most PUS services were created for communication between onboard applications and ground systems. JAS adds additional services to support more onboard payload functions. [Placeholder: Additional development is needed to define the JAS specific services to support onboard payload...
JAS Telemetry Packet
Specification • JAS Telemetry Packet All fields are shown in bits. The variable length application data field must be an integral number of bytes for the packet error control calculation. Spare bits may be used for padding purposes at the end to ensure the packets are an even number of bytes in...
JAS Toolbox Introduction
Other • The JAS standard is captured in the JAS Toolbox, and presented using a web-based content management system known as the Interactive Standards Publication Tool (ISPT). In addition to the JAS standard, the JAS Toolbox includes a set of Systems Engineering (SE) Tools, which provide system examples and modeling capabilities. The...
JAS versus PROPIN Trade Study
Other • Feature Comparison JAS has a number of positive impacts on budget, schedule, and performance. Below is a table that illustrates these advantages when comparing a JAS-based system to a PROPIN approach. Advantage Benefit Budget Schedule Performance Scalable processing systems Ability to add/remove as many nodes as are needed to support...
JEEP Packet Format
Specification • All JEEP packets shall include a fixed length header, followed by a variable length payload. The figure below shows how the JEEP packet is embedded within the standard SpaceWire packet. Note that while a SpaceWire packet may have zero or more destination addresses before the JEEP header, the JEEP requires...
Joint Architecture Standard Overview
Other • The purpose of JAS is to realize a reusable set of common hardware and software module designs that can be easily scaled, configured, adapted, interconnected and integrated with industry standards and internally supported intellectual property (IP) to provide the functionality needed to support any payload sensor suite. JAS also provides...
JRDDP Packet Format
Specification • All JRDDP packets shall include a variable length header, followed by a variable length payload, followed by a 2-byte CRC Trailer. The figure below shows how the JRDDP packet is embedded within the standard SpaceWire packet. Note that while a SpaceWire packet may have zero or more destination addresses before...
Junction Temperatures
Specification • The design shall show positive margin against thermal design so junction temperatures do not exceed maximum component values for worst case orbits at beginning (BOL) and end of life (EOL).
Life
Specification • The JAS mechanical structure shall be constructed of materials capable of performing for the necessary mission life time (for example, 3 years storage in an inert atmosphere and 10 years on orbit). This analysis will require extensive parts and materials screening and processing.
Loads
Specification • Loads shall be determined per the program Strength Qualification Plan.
Local POL Power Conversion
Profile • PS Node Local POL Conversion The output power from the PS node is one or more secondary voltage rails that are distributed throughout the system. This distributed secondary voltage is typically a higher voltage than those required by the components on the other nodes in order to improve efficiency by...
Local Power Conversion and Control
Profile • SMAC Local Power Conversion and Control The input power for the SMAC is provided by a single voltage rail that is distributed throughout the system and delivered to nodes. The power for the SMAC shall default to an “on” state for at least one node in the system when the...
Logical Connections
Specification • Upon initialization all TEPs shall be in the CLOSED state. OPEN/RESET Command When a transmit TEP transitions to the ENABLED state (as commanded by the host), it shall send an OPEN/RESET packet to its receive TEP and initiate an acknowledgement timer. CLOSE Command When a transmit TEP transitions to the...
MAGE Strength
Specification • The JAS mechanical structure shall consider tooling to hold it while installing and transporting components. Features for mounting the hardware that supports the system shall be included. A static 4 G load shall be used with positive margins per this document. Mechanical Aerospace Ground Equipment (MAGE)
Margins of Safety
Specification • Margin of Safety (MS) is defined as MS = 1/R - 1, where R is the ratio of the factored applied load (or stress) to the allowable load (or stress) and shall be greater than 0. Margin of Safety Calculation The specific failure theory used to determine the allowable load...
Mass Properties
Specification • The JAS mechanical structure shall attempt to optimize mass, center of gravity, and moments of inertia.
Material Properties and Allowables
Specification • The JAS mechanical structure design of the metallic parts shall use A Basis allowables from MIL-HDBK-5 or equivalent. The design of the composite parts shall use B Basis allowables generated using the methodology in MIL-HDBK-17 or equivalent.
Materials
Specification • The JAS mechanical structure shall be constructed of materials capable of performing at the specified orbit for a minimum of ten years after being stored in an inert gas environment and after exposure to clean air during testing, launch, and ascension. The use of the following materials is prohibited: Zinc,...
Mechanical
Profile • The recommended CH implementation is on a 6U VPX board, as defined in the VITA 46 standard and the Mechanical Specification. VPX is preferred for a number of reasons, a few of which include: 3U and 6U board formats to accommodate varying sizes High-density connectors and flexible pinout Availability of...
Mechanical
Profile • Exact mechanical specifications will vary widely depending on the type of module and the location where it will be integrated into the system. However, there are two predominant applications for the expansion module: a mezzanine board for CH or RP profiles or a RTM to attach to a backplane. Mezzanine...
Mechanical
Profile • The recommended PS implementation is on a 6U VPX board, as defined in the VITA 46 standard and the Mechanical Specification. VPX is preferred for a number of reasons, a few of which include: 3U and 6U board formats to accommodate varying sizes High-density connectors and flexible pinout Availability of...
Mechanical
Profile • The recommended RP implementation is on a 6U VPX board, as defined in the VITA 46 standard and the Mechanical Specification. VPX is preferred for a number of reasons, a few of which include: 3U and 6U board formats to accommodate varying sizes High-density connectors and flexible pinout Availability of...
Mechanical Interface Design
Specification • The JAS mechanical structure as described in this Mechanical specification will support applications intended for a space environment and will provide stable mechanical structure for the electronics during launch and while operating in a high vacuum.
Mechanical Specification
Specification • The Mechanical Specification provides details about mechanical interface design, environmental impacts, and design constraints that should be considered for implementing mechanical structures in a JAS-based system. The figure below provides context of where the Mechanical Specification resides in the JAS standard. JAS Standard Hierarchy
Megabit Interfaces
Profile • There are several megabit interfaces that may be utilized on the CH node. Some examples of these include: SpaceWire RS-422, RS-232 MIL-STD-1553 CAN bus SpaceWire is the preferred solution for systems requiring data rates below 200 Mbps. SpaceWire links can scale from 2 to 200 Mbps at full duplex and...
Megabit Interfaces
Profile • There are several megabit interfaces that may be utilized on the RP node. Some examples of these include: SpaceWire RS-422, RS-232 MIL-STD-1553 CAN bus SpaceWire is the preferred solution for systems requiring data rates below 200 Mbps. SpaceWire links can scale from 2 to 200 Mbps at full duplex and...
Megabit Interfaces
Profile • There are several megabit interfaces that may be utilized on the RP node. Some examples of these include: SpaceWire RS-422, RS-232 MIL-STD-1553 CAN bus SpaceWire is the preferred solution for systems requiring data rates below 200 Mbps. SpaceWire links can scale from 2 to 200 Mbps at full duplex and...
Megabit-class Interfaces
Profile • There are several megabit-class interfaces that may be utilized on the PS node. Some examples of these include: SpaceWire RS-422, RS-232 MIL-STD-1553 CAN bus SpaceWire is the preferred solution for systems requiring data rates below 200 Mbps. SpaceWire links can scale from 2 to 200 Mbps and are well suited...
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...
Memory Access Service
Specification • Error: unable to migrate element with tag="" The following diagram shows how the JAS Memory Access Service fits into the overall communication stack. The Memory Access Service provides a standard interface to applications that allows them to remotely access memory on a JAS node across a communication link. This is...
Memory Storage
Profile • Another possible instantiation of this profile is to include non-volatile memory and/or SRAM/SDRAM storage on a CH or RP node. Memory Storage Instantiation
Memory Technologies
Profile • There are two types of memory technologies that are highly recommended for inclusion on the CH node: non-volatile flash or EEPROM, and higher-speed SRAM or SDRAM memory. Non-volatile memory is necessary to store the software that the microprocessor will execute upon power-up. Non-volatile memory may also be necessary to store...
Memory Technologies
Profile • RP Node Memory Technologies External memory is often included on RP node instantiations to support the FPGA’s processing. Among other uses, memory provides storage for sensor data and working space to implement processing algorithms. Any combination of memory technologies, including Synchronous Dynamic Random Access Memory (SDRAM), Static Random Access Memory...
Mezzanine Connector
Specification • A very useful option for plug-in modules is the ANSI/VITA 57 standard FPGA Mezzanine Card or FMC. This standard specifies an industry standard form factor utilizing a low profile, high-speed, high-pin count connector. The FMC connector can support very high bandwidths. The FMC approach solves the problem of how to...
Microprocessor
Profile • The CH Node is a microprocessor-based node that executes software stored in supplemental on-board memory. It is highly recommended that this microprocessor be radiation-hardened for reliability. The processor is typically attached to a non-volatile memory technology and a faster SRAM or SDRAM memory. A bus interface between the microprocessor and...
Mission Data Processing
Profile • This application employs the CH node as a mission data processor, utilizing the radiation-hardened microprocessor and on-board memories to perform computations in support of the payload’s mission. Additional optional memories or other board capabilities may be built onto the expansion port if desired. Mission Data Processing Instantiation This application is...
Molecular Contamination
Specification • For all components that will be in the vicinity of an optical payload and anywhere that contamination at the molecular level is an issue, all parts and materials must comply with ASTM E 595 for less than 1% Total Mass Loss (TML) and 0.1% CVCM. Thermal bake-out of all components...
Molecular Thermovac Testing
Specification • Thermovac temperature testing is required to determine dissipation at full power modes. A test plan needs to be developed and coordinated with the System Engineer.
Mounting Distortion Impact
Specification • The JAS mechanical structure shall maintain the electronics/PCBs listed below within given positions with distortions less than expected for the intended application.
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...
Multiplexed Logical Channels
Specification • The protocol shall support multiple simultaneous logical connections over a single SpaceWire link.
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...
Network Interfaces
Profile • All JAS nodes communicate through a standard set of interfaces that adhere to standard protocols. Refer to the Electrical Specification for physical layer technical information and Communication Specification for details on standard data protocols. This section describes two classes of network interfaces, megabit interfaces with line speeds below one gigabit...
Network Interfaces
Profile • All JAS nodes communicate through a standard set of interfaces that adhere to standard protocols. Refer to the Electrical Specification for physical layer technical information and Communication Specification for details on standard data protocols. This section describes megabit-class interfaces, with line speeds below one gigabit per second ( The protocols...
Network Interfaces
Profile • All JAS nodes communicate through a standard set of interfaces that adhere to standard protocols. Refer to the Electrical Specification for physical layer technical information and Communication Specification for details on standard data protocols. This section describes two classes of network interfaces, megabit interfaces with line speeds below one gigabit...
Network Interfaces
Profile • All JAS nodes communicate through a standard set of interfaces that adhere to standard protocols. Refer to the Electrical Specification for physical layer technical information and Communication Specification for details on standard data protocols. This section describes two classes of network interfaces, megabit interfaces with line speeds below one gigabit...
Network Router
Profile • SMAC Network Router The network interface implemented by the SMAC is typically SpaceWire, though other protocols may be implemented. It is highly recommended to implement a network router (rather than just endpoints) in order to provide redundancy in the network and better choices of network topologies. Configurable routers also permit...
Network Topologies
Other • The selection of network topology is a critical component when developing multi-node or multi-point system architectures. A good choice of topology will require less power, have less complexity, higher reliability, and will orchestrate network traffic smoothly and quickly between nodes. Conversely, a poor choice of topology will introduce complex and...
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...
Node Personality
Profile • SMAC Personality NV Memory A NV memory should be connected to the SMAC. The NV memory is used for two purposes: storing initial SMAC configuration information, and storing personality information about the node. The stored SMAC configuration typically consists of default routing tables for the network router, processing element power...
Nominal Case
Specification • In the nominal case the close packet is immediately acknowledged by the receive TEP and the transmit TEP transitions to the CLOSED state. The receive TEP transitions to the CLOSED state after the expiration of its timer. The purpose of the receive TEP’s delay in the CLOSING state is to...
Non-Volatile Memory Storage
Profile • Another common application of this profile is as an interface to non-volatile memories. These memories may contain firmware for FPGA nodes, mission data queued for transmission to the ground, payload configuration parameters, software, and more. Non-Volatile Memory Storage Instantiation In these applications, the CH node software is configured with services...
Obscuration
Specification • All JAS mechanical structure components shall be placed to prevent obscuration of the system view of space if the JAS electronics box will be used to radiate. Structural elements shall be kept an appropriate distance away from the JAS electronics housings.
Operating Temperatures
Specification • Operational temperatures are provided in thermal study for the nominal orbit. Excursions from predicted operational temperatures shall be increased by 11C (bilateral) when these temperatures are utilized in all fatigue analysis. For the purposes of fatigue the temperature excursion within an orbital season may be considered. For the purposes of...
Operational Vibrations
Specification • The JAS housing shall meet all of the displacement budgets, while subjected to the operational environment produced by the acceleration in file, TBD. These shall be used as base inputs.
Orientation
Specification • The JAS housing shall meet mechanical alignment performance specifications in any direction.
Overall Functional Description
Specification • This protocol describes the mechanism for reliable transfer of data packets over a SpaceWire connection and adds the following capabilities to a SpaceWire link: Multiplexed Logical Connections Reliable Delivery Missing packet detection Out of sequence packet reordering Buffer fragmentation and reassembly
Packaging for Thermal Dissipation
Specification • The preliminary JAS mounting details are defined by the baseplate details in ICD drawing xxxxxx. The JAS electronics box is meant to mount through the blue baseplate shown in the figure below. The figure shows a nominal 3x3 stack in an exploded view. JAS Mounting Exploded View Conducted Self-radiated panels...
Packet Addressing and Routing
Specification • Packets will be identified and routed in the system using the SAPID, DAPID, ST, and SST. Applications shall provide these fields to the JAS Packet Service to create the stream of packets that will be sent across the communication channel. Communication channels and addresses, such as a SpaceWire address, can...
Packet Error Control
Specification • Even though JAS network protocols offer a guaranteed delivery option, there still exists the possibility of an error being introduced into a packet while it is being created or transferred from memory to the communication channel. To provide an additional layer of error detection all JAS packets shall contain a...
Packet Sequence Numbers
Specification • An 8-bit sequence number shall be assigned to each packet transmitted.
Packet Sequencing
Specification • The use of the packet sequencing fields within the JAS packet is different from the definition in the CCSDS and PUS standards. The original intention of the packet sequence counter was to provide two functions. First, it was used in combination with the sequence flags to reassemble data sets that...
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...
Packet Service Definitions
Specification • [Placeholder: services reserved for and specific to JAS; this is a lead in to describe the services. Contact SNL if immediate support is needed with this topic. Content will be developed for JT 2.0.]
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...
Particulate Contamination
Specification • Internal Cavities will be wiped clean with isopropyl alcohol and allowed to air dry for 30 minutes prior to close out; the structure will be covered during the drying process. The surfaces will be visibly clean. Visibly clean is defined as no contamination visible when viewed from 6-18 inches away...
Payload
Specification • JRDDP Packet Format Secondary Header (Optional) The presence of the optional secondary header is indicated by the Secondary Header Flag in the Packet Control field. If a secondary header is present, its contents and format are implementation dependent and shall be documented in a program specific document. The secondary header...
PCI Express
Specification • PCI Express, or PCIe, is another multi-lane high speed serial interconnect technology. Each lane is a full-duplex data stream comprised of two differential signaling pairs, one for transmitting and one for receiving.
Platform Management Service
Specification • The platform management service, service type address 130 is used to configure, manage, and monitor network specific resources. The currently defined platform management service parameters are shown in the following table. Service Type Service Subtype Subtype Description Cmd Tlm Service Parameters Data Types and Description 130 11 Network Topology Upload...
Potential Flight Capability
Specification • Each component of the JAS mechanical structure should consider Flight capability as this will force consideration of design, flight, and test environments described in this specification. The JAS mechanical structure should be designed for the specific application intended.
Power Conversion
Profile • The input power for CH nodes is provided by one or more voltage rails that are distributed throughout the system. This distributed voltage is typically a higher voltage than those required by the components on the board in order to improve efficiency by minimizing losses through distribution. The CH node...
Power Conversion
Profile • RP Node Power Conversion The input power for RP nodes is provided by a single voltage rail that is distributed throughout the system. This distributed voltage is typically a higher voltage than those required by the components on the board (typically +5 volts) in order to improve efficiency by minimizing...
Power Distribution Architecture
Specification • JAS will accept at least one primary input power source supplied to the system. The primary input power will connect directly to the Power Supply or PS node in a JAS arrangement. The PS node converts the primary input voltage to a lower voltage which is then sent to all...
Power Supply Profile
Other • The PS profile defines a high-performance power solution, suitable for powering JAS nodes. The PS profile works alongside other nodes within the JAS architecture. The SMAC and Communications profile implement connectivity and data transfer from PS nodes to other nodes in the system. Power Supply Node The figure below illustrates...
Power Supply Profile
Profile • The PS profile defines a high-performance power solution, suitable for powering JAS nodes. The PS profile works alongside the CH and RP profiles to implement groups of nodes (i.e., boxes) within the JAS architecture. The SMAC and Communications profile implement connectivity and data transfer from PS nodes to other nodes...
Pressure
Specification • The JAS structure shall meet all performance specifications during and after exposure to pressures varying from atmospheric to the space environment of 10-14 Torr. All thermal-vacuum ground based testing shall be conducted at pressures less than 10-6 Torr.
Pressure Change
Specification • The structure shall be designed to survive the change of pressure specified in the figure below. The launch and ascent pressure environment will lie between Pc(Max) and Pc(MIN). Pressure Change Within the envelope defined in figure above, the local rates of change will remain between the values shown in the...
Primary DC to DC Conversion
Profile • PS Node DC-DC Converters The PS node utilizes isolated DC-DC switching converter devices, which provide the primary power conversion capability for this node type. The DC-DC converter converts the primary bus voltage to a regulated secondary voltage that is distributed to the nodes in the system.
Primary Power Conversion
Specification • JAS will provide the capability to convert primary power to secondary power.
Primary Power Conversion Efficiency
Specification • The converter should be optimized for efficiency to reduce power consumption and avoid unnecessary heat generation through power dissipation. The exact design of the primary converter will depend upon the required efficiency and the exact nature of the input power.
Primary Power Conversion Galvanic Isolation
Specification • The primary power converter should provide galvanic isolation between the primary power and the secondary power.
Primary Power Conversion Noise Reduction
Specification • The converter should reduce or eliminate noise and/or fluctuations in the primary input power.
Primary Power Redundancy
Specification • JAS will implement the application requirements for primary power supply redundancy.
Processing Logic
Profile • RP Node Processing Logic The RP node utilizes a Field-Programmable Gate Array (FPGA) device which provides the primary processing capability for this node type. FPGAs offer customization of the processing logic allowing the RP node to function for a variety of applications. Reprogrammable FPGAs are preferred over one-time-programmable (OTP) FPGAs...
Processing Logic
Profile • SMAC Processing Logic The SMAC utilizes a radiation-hardened, non-volatile FPGA device to provide the primary processing capability for SMAC functions. This FPGA shall always be powered on when system power is applied regardless of the power state of the remainder of the node. It is recommended to use local POL...
Protocols
Specification • The protocols described in the following sections are used for various SpaceWire applications depending on the needs of the communication interface. Remote Memory Access Protocol (RMAP) is a SpaceWire standard used for memory access. JAS Efficient Exchange Protocol (JEEP) and JAS Reliable Data Delivery Protocol (JRDDP) are both specific to...
Quasi-Static Loads
Specification • Quasi-static loads shall be applied per the program Strength Qualification Plan. The axial and radial acceleration loads are to be applied simultaneously for an 11 g (TBD?) load in the worst case direction.
Radiation Effects Mitigation
Specification • The primary space effect requiring mitigation is the radiation environment, which causes gradual degradation of electronic devices and single event effects (SEE). Parts that have demonstrated destructive SEE, such as SEL or SEGR, should not be incorporated into the node unless absolutely necessary. It is equally important to test the...
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...
Rear Transition Module
Profile • This instantiation provides a breakout for backplane signals per the VITA 46.10 specification. A rear transition module (RTM) attaches to the back side of a backplane directly behind and in-line with a front plug-in module (usually a node). The RTM provides accessibility to signals such as communication breakouts, power connectivity,...
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