Svc/Ccsds/SpacePacketDeframer/docs/sdd.md
The Svc::Ccsds::SpacePacketDeframer is an implementation of the DeframerInterface for the CCSDS Space Packet Protocol.
It receives data containing a Space Packet on its input port and extracts the Space Packet. Please refer to the CCSDS Space Packet Protocol specification (CCSDS 133.0-B-2) for details on the packet format.
The Svc::Ccsds::SpacePacketDeframer is typically used downstream of a component that removes transfer frame headers, such as the Svc::Ccsds::TcDeframer. It validates the Space Packet header and extracts the payload.
The Svc::Ccsds::SpacePacketDeframer extracts the following fields from the CCSDS Space Packet Primary Header and populates them in the output FrameContext:
| Field | Context Field | Description |
|---|---|---|
| Application Process Identifier (APID) | apid | Extracted from bits [10:0] of the Packet Identification field. Invalid APID values (per ComCfg::Apid::isValid()) are mapped to INVALID_UNINITIALIZED. |
| Secondary Header Flag | hasSecHdr | Extracted from bit [11] of the Packet Identification field |
| Sequence Flags | sequenceFlags | Extracted from bits [15:14] of the Packet Sequence Control field (0b00=Continuation, 0b01=First, 0b10=Last, 0b11=Unsegmented) |
| Packet Sequence Count | sequenceCount | Extracted from bits [13:0] of the Packet Sequence Control field |
| Kind | Name | Port Type | Description |
|---|---|---|---|
| Input (guarded) | dataIn | Svc.ComDataWithContext | Port to receive data containing a Space Packet |
| Output | dataOut | Svc.ComDataWithContext | Port to output the extracted Space Packet payload |
| Output | dataReturnOut | Svc.ComDataWithContext | Port for returning ownership of received buffers |
| Input (sync) | dataReturnIn | Svc.ComDataWithContext | Port receiving back ownership of sent buffers |
| Output | validateApidSeqCount | Ccsds.ApidSequenceCount | Port to request validation of a sequence count for a given APID |
| Output | errorNotify | Ccsds.ErrorNotify | Port to send notification of deframing errors |
| Name | Severity | Description |
|---|---|---|
| InvalidLength | warning high | Deframing received an invalid packet length |
| InvalidPacket | warning high | Deframing received a malformed packet |
| Name | Description | Validation |
|---|---|---|
| SVC-CCSDS-SPD-001 | The SpacePacketDeframer shall deframe CCSDS Space Packets according to the CCSDS 133.0-B-2 standard. | Unit Test, Inspection |
| SVC-CCSDS-SPD-002 | The SpacePacketDeframer shall extract the user data field from valid Space Packets. | Unit Test |
| SVC-CCSDS-SPD-003 | The SpacePacketDeframer shall validate the packet length of a Space Packet Primary Header. | Unit Test |
| SVC-CCSDS-SPD-010 | The SpacePacketDeframer shall validate the Packet Version Number field and reject packets whose Packet Version Number does not match the CCSDS Space Packet Protocol, emitting InvalidPacket and returning the buffer. | Unit Test |
| SVC-CCSDS-SPD-009 | The SpacePacketDeframer shall emit an InvalidLength event if the packet length token in the header is cannot fit in the received data, and drop the received packet. | Unit Test |
| SVC-CCSDS-SPD-004 | The SpacePacketDeframer shall receive incoming data containing Space Packets via the dataIn port. | Unit Test |
| SVC-CCSDS-SPD-005 | The SpacePacketDeframer shall output the extracted Space Packet user data via the dataOut port. | Unit Test |
| SVC-CCSDS-SPD-006 | The SpacePacketDeframer shall manage buffer ownership using the dataReturnIn and dataReturnOut ports. | Unit Test, Inspection |
| SVC-CCSDS-SPD-007 | The SpacePacketDeframer shall delegate sequence count validation to another component through the validateApidSeqCount port. | Unit Test |
| SVC-CCSDS-SPD-008 | The SpacePacketDeframer shall perform sequence count validation for APIDs registered via validateApidSeqCount. | Unit Test |
| SVC-CCSDS-SPD-009 | The SpacePacketDeframer shall emit notifications on its errorNotify port when deframing errors occur. | Unit Test |