Specification • The Communication Specification provides details about network interfaces, communication services, and packet structures that were described in the Communication Profile. The figure below provides context of where the Communication Specification resides in the JAS standard. JAS Standard Hierarchy
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Communications Profile
Other • The Communications Profile defines standard interfaces for facilitating communication between nodes within a JAS system. The Communications Profile focuses primarily on communication between payload applications. It leverages industry standards to support network-based communication using serial interfaces. Adherence to the Communications Profile and Communications Specification is the minimum required for a...
Companion Field Programmable Gate Array
Profile • A separate radiation-hardened companion FPGA is present on the CH node to implement timing functions, custom peripherals, and bridge to proprietary interfaces that may not be directly supported by the microprocessor. The FPGA typically attaches to the microprocessor through industry-standard bus interfaces, though the exact connection method will vary based...
Complete and Incomplete Hypercubes
Other • An overall good performer, hypercubes are very reliable and offer good performance. Complete hypercubes have fixed size of 2^d (i.e., 4, 8, 16, 32, 64, etc, nodes) but an extension to this structure (incomplete hypercubes) allows for arbitrary size. Hypercubes are constructed by beginning with two interconnected nodes (a 1-D...
Coordinate Definition
Specification • The JAS mechanical structure shall implement a coordinate system as a reference point for the design. The mounting of each component should be considered as the coordinate reference. The coordinate frame can originate on a pin-and-slot mounting. [Placeholder: Defining a coordinate frame helps to determine center of gravity, mass, envelopes...
Cube Connected Cycles
Other • Cube-connected cycles (CCC) are structures based on hypercubes (see Figure). Given a hypercube of dimension d, each hypercube node is replaced with a ring of size d. This causes the node degree of all nodes to be fixed at 3 regardless of network size! This structure excels when the port...
Custom Communications
Specification • Custom communications specifications by definition are not described by any single specification. The electrical parameters will be determined by the components involved in the design. For example, if the communications utilize gigabit (GTX) transceivers in an FPGA then the electrical requirements will be prescribed by the GTX specifications.
Data Transmit Queue
Specification • When packets from more than one channel are available for transmit, packets shall be transmitted in the order in which they are queued and in accordance with the transmit priority described above.
Data Types
Specification • The JAS standard does not require a specific length or encoding format for data types. Systems can define these based on what best suits their needs. Sizes, endianness, byte ordering, and bit ordering are typically driven based on the processing and memory architectures that are used. However, in order to...
Delayed Case
Specification • A delayed but recoverable scenario occurs when a receive TEP receives at least one CLOSE packet but the transmit TEP does not receive any ACK packets as shown in Figure 3. In this case the receive TEP will eventually transition to the CLOSED state via the timeout and the transmit...
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