- !Packet
  name: CCSDS_HEADER
  fields:
    - !Field
      name:       version
      desc:       Indicates CCSDS Version-1 (does not change)
      bytes:       0
      type:       U8
      mask:       0xE0
    - !Field
      name:       type
      desc:       |
        Distinguishes between core and payload packet types to extend the
        APID space to 4032
      bytes:       0
      type:       U8
      mask:       0x10
      enum:
        0: 'Core'
        1: 'Payload'
    - !Field
      name:       secondary_header_flag
      desc:       |
        Indicates whether, or not, a Secondary Header follows the primary
        header (always set to 1)
      bytes:       0
      type:       U8
      mask:       0x08
      enum:
        0: 'Not Present'
        1: 'Present'
    - !Field
      name:       apid
      desc:       |
        Used in conjunction with Type to define the Logical Data Path
      bytes:       [0, 1]
      type:       MSB_U16
      mask:       0x07FF
    - !Field
      name:       sequence_flags
      desc:      |
        When sending commands, the sequence flags must be marked as
        unsegmented data. All other PL packets may be per source/destination
        ICDs.
      bytes:       2
      type:       U8
      mask:       0xC0
      enum:
        0: 'Continuation Segment'
        1: 'First Segment'
        2: 'Last Segment'
        3: 'Unsegmented'
    - !Field
      name: sequence_count
      desc:      |
        Sequential count which numbers each packet on a Logical Data Path,
        i.e. a separate counter is maintained for each source-destination
        pair.
      bytes: [2, 3]
      mask: 0x3FFF
      type: MSB_U16
    - !Field
      name: packet_length
      desc:      |
        Sequential count which expresses the length of the remainder of the
        packet including checkword if present. The value is the number of
        bytes (octets) following the field minus 1.
      bytes: [4, 5]
      type: MSB_U16
    - !Field
      name: time_coarse
      desc: |
        The Time Code is made up of a preamble field (P-field) and a time
        field (T-field). For ISS, as allowed by the CCSDS Recommendation, 
        the P-field is implicitly conveyed (it is not present with the
        T-field). ISS time is referenced to GPS Time (midnight 5-6 January 
        1980). The T-field consists of 4 octets of coarse time and 1 octet of
        fine time. These octets are a set of binary counters, cascaded with
        the adjacent counters. The value represents the elapsed time since
        midnight 5-6 January 1980. The least significant bit (LSB) of the
        least significant octet of coarse time is equal to 1 second.
      bytes: [6, 9]
      type: TIME32
    - !Field
      name: time_fine
      desc: |
        The LSB of the fine time octet is equal to 2-8 second, or about 4 ms.
      bytes: 10
      type: TIME8
    - !Field
      name: time_id
      desc: |
        The time field is always present. This field indicates its use.
        Commands with Time ID = 00 indicate real-time commands (RTC) which are
        not authenticated, e.g., commands originating from the Orbiter. Cmds
        with ID = 01 are RTC commands for which authentication is required,
        e.g., commands to the USOS from the SSCC. Commands with ID = 10 are
        stored in the C&C MDMs time-tagged command queue for later execution.
        For Data Packets, the field is always 01 and the time fields contain
        the time at the beginning of the processing frame when the packet was
        generated.
      bytes: 11
      type:  U8
      mask: 0xC0
      enum:
        0: 'Not Used'
        1: 'Data Gen'
        2: 'Time Tagged Cmd'
        3: 'Invalid'
    - !Field
      name: checkword_indicator
      desc: |
        This field indicates if a checkword (add without carry checksum) is
        contained in the CCSDS packet. When present, the checkword is the last
        16-bit word of the packet. All commands must contain a checkword. Data
        packets do not contain a checkword.
      bytes: 11
      type:  U8
      mask: 0x20
      enum:
        0: 'Not Present'
        1: 'Present'
    - !Field
      name: zoe
      desc: |
        Used in a telemetry data packet to indicate that the telemetry packet
        is from the onboard ZOE recording.
      bytes: 11
      type:  U8
      mask: 0x10
      enum:
        0: 'Onboard recording'
        1: 'All Other Cases'
    - !Field
      name: packet_type
      bytes: 11
      type:  U8
      mask: 0x0F
      enum:
        1:  'Data Dump'
        4:  'Telemetry Status'
        6:  'Payload Private Science'
        7:  'Ancillary Data'
        8:  'Essential Command'
        9:  'System Command'
        10: 'RT/Payload Command'
        11: 'Data Load'
    # - !Field
    #   name: spare
    #   bytes: 12
    #   mask: 0x80
    - !Field
      name: element_id
      bytes: 12
      type:  U8
      mask: 0x78
      enum:
        0:  'NASA 0'
        1:  'NASA 1'
        2:  'ESA/APM'
        3:  'NASDA'
        4:  'RSA'
        5:  'CSA'
        6:  'ESAATV'
        7:  'ASI'
        8:  'ESA/ERA'
        9:  'Reserved'
        10: 'SPP'
        11: 'HTV'
        # 12: 'Spare 0'
        # 13: 'Spare 1'
        # 14: 'Spare 2'
        # 15: 'Spare 3'
    - !Field
      name: data_packet
      desc: |
        Identifies this field as a data packet. This field distinguishes
        between command and data packets and is used to ensure unique
        definition of the 32- bit USOS Packet ID field.
      bytes: 12
      mask: 0x04
      type: U8
    - !Field
      name: version_id
      desc: |
        Configuration Management. Used to identify multiple versions
        of a format.
      bytes: [12, 13]
      mask: 0x03C0
      type: MSB_U16
    - !Field
      name: format_id
      desc: Identifies the packet.
      bytes: 13
      mask: 0x3F
      type: U8
      enum:
        0: Reserved
        1: 'Essential Telemetry'
        2: 'Housekeeping Tlm-1'
        3: 'Housekeeping Tlm-2'
        4: 'PCS DDT'
        5: 'CCS S-Band Command Response'
        6: 'Contingency Telemetry to SMCC'
        7: 'Normal Data Dump'
        8: 'Extended data Dump'
        9: 'MSS Ancillary Data'
        10: 'Reserved'
        11: 'Broadcast Ancillary Data'
        12: 'PCS Status'
        13: 'NCS to OIU Telemetry and ECOMM telemetry'
        14: 'CCS to OIU Telemetry - Direct'
        15: 'SM to USOS Status Data'
        16: 'Normal File Dump'
        17: 'Extended File Dump'
        18: 'NCS to FGB Telemetry'
        19: 'EMU Suit Data'
        20: 'ZOE Normal Dump (S- Band)'
        21: 'ZOE Extended Dump (S- Band)'
        22: 'EMU S-Band TLM Packet'
        23: 'VTC1 to CCS Status Packet'
        24: 'VTC2 to CCS Status Packet'
        25: 'MMC to CCS Status Packet'
        26: 'CCS to OIU Telemetry via UHF'
        # 27-63 reserved
    # - !Field
    #   name: spare
    #   bytes: [14, 15]
    #   mask: 0x3F
    #   type: U8
    - !Field
      name: frame_id
      desc: |
        Identifies the processing frame count of the frame in which the data
        packet was built. Not applicable for extended dump and data dump
        packets.
      bytes: 15
      mask: 0x7F
      type: U8