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Acknowledgement and Retransmit

Specification • The receiver shall send a positive acknowledgment (ACK) packet for each DATA packet received without error.

Communication Specification > SpaceWire > Protocols > JAS Reliable Data Delivery Protocol > Overall Functional Description > Acknowledgement and Retransmit

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

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

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...

Communication Specification > SpaceWire > Protocols > JAS Efficient Exchange Protocol > Buffer Segmentation 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

Channel Independence

Specification • Each transport channel shall operate independently from other transport channels.

Communication Specification > SpaceWire > Protocols > JAS Reliable Data Delivery Protocol > Overall Functional Description > Channel Independence

Channel Operations

Specification •

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

Communication Specification

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

Communication Specification

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.

Communication Specification > SpaceWire > Protocols > JAS Reliable Data Delivery Protocol > Overall Functional Description > Data Transmit Queue

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...

Communication Specification > JAS Packets > JAS Packet Definition > Data Types

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...

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

Device Access Service

Specification • The device access service, service type address 128, is used to request parameters from or command parameters to a specific device. The currently defined device access service parameters are shown in the following table. Service Type Service Subtype Subtype Description Cmd Tlm Service Parameters Data Types and Description 128 1...

Communication Specification > JAS Packets > Packet Service Definitions > JAS Specific Services Definitions > Device Access Service