Specification • The primary power converter should provide galvanic isolation between the primary power and the secondary power.
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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.
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...
Rear Transition Module
Specification • The rear transition module (RTM) of the VPX standard is a plug-in module at the back of the circuit card chassis that is in line with the front plug-in module or node. The backplane connectors on the RTM are the same as those used on the plug-in nodes. Also, as...
Receive TEP Operations
Specification • A receive TEP shall not send DATA or CONTROL packets. It may only send ACK packets. Sliding Window The receive TEP shall maintain a sliding window, which is a range of consecutive sequence numbers that is used to determine whether each received DATA packet will be accepted or discarded. The...
Reliable Delivery
Specification • JRDDP detects lost packets, duplicate packets, out of sequence packets, and provides damaged data recovery. The protocol provides additional error detection beyond the SpaceWire physical layer by utilizing Cyclic Redundancy Checks (CRCs), packet sequence numbers, positive acknowledgement, and timeouts to detect lost or duplicated Data packets.
Remote Memory Access Protocol
Specification • JAS should use the RMAP standard to remotely access memory devices across the SpaceWire network.
Retransmission
Specification • If an ACK packet is not received by the transmit TEP within a defined channel-specific timeout interval the DATA packet shall be retransmitted.
Screened Venting
Specification • Where venting requires a screen to maintain cleanliness requirements, based on a 5µ Pall Rigidmesh screen, there shall be 1.5 in^2 or greater screen area per ft^3 of volume where the volume is the sum of multiple daisy-chained volumes. The daisy chained volumes shall be vented.
Secondary POL Conversion
Specification • JAS nodes should include POL conversion as needed. POL conversion has become very popular as the voltage requirements of electronic components have continued to drop. It is quite common for many digital electronic devices to use voltages of 1.8 VDC and below. Routing high current, low voltages around a printed...
Sequence Number Use
Specification • At the receiver TEP the sequence numbers shall be used to detect lost data packets, duplicate packets and to correctly order packets.
Serial RapidIO
Specification •
Serial RapidIO
Specification • Serial RapidIO (or just RapidIO) is a high-performance packet-switched, interconnect technology utilizing either 8b/10b or 64b/67b encoding on data links, or lanes, with speeds up to 6.25 Gbps. Multiple lanes may be used in increase data throughput.
Shielding
Specification • The JAS mechanical structure shall provide EMI shielding which meets 60db shielding effectiveness from 0.1 to 1 GHz for the FPA Sensor box with covers in place.
Space VPX
Specification • While no specific node-to-node interconnection method is specified in JAS it is highly recommended that the nodes make use of a standards-based chassis and backplane. SpaceVPX is similar to VPX but intended for space applications. [Placeholder: There may be sub-specs we can reference here, similar to the subspecs for VITA...
Space Wire
Specification • SpaceWire is a full-duplex, point-to-point, serial data communications protocol in which the data is encoded on two differential signal pairs in each direction. This is the preferred JAS communication protocol for data rate below 200 Mbps. The electrical specifications for SpaceWire communications are described in the European Cooperation for Space...
SpaceWire
Specification • The figure below defines the format of the SpaceWire packet. Following sections will discuss the details of SpaceWire Addressing, Protocol Identifiers, and the various protocols that have been developed using SpaceWire for JAS. SpaceWire Packet
SpaceWire Addressing
Specification • SpaceWire addresses shall follow the allowed allocation defined in the SpaceWire standard. Only logical addresses will be used for router and endpoint addresses which means they must be in the range of 0x20-0xFE. JAS applications shall use SpaceWire regional addressing in conjunction with header deletion within the SpaceWire routers. Two...
SpaceWire Protocol Identifiers
Specification • The standard reserves protocol identifiers in the range of 1 to 239. Protocol identifiers in the range of 240-255 can be assigned by projects. The protocol identifiers ranging from 240-250 shall be reserved for JAS protocols. A list of the protocols used by JAS is shown in the table below....
Strength Qualification
Specification • The JAS mechanical structure design shall possess sufficient strength and rigidity to withstand environmental conditions defined in this document. Load Conditions
Structural Integrity
Specification • The JAS mechanical structure design shall possess sufficient strength and rigidity to withstand environmental conditions defined in this document.
Subnetwork Services
Specification • JAS Subnetwork Services provide a set of well-defined interfaces for applications to communicate across a network. They provide a layer of abstraction between the applications and the network protocols and data links, thereby allowing applications to be more portable and reusable. The services use a combination of a standard application...
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