"CCSDS telecommand header (bytes 0-1)" (SVC/ITC)

View Options: (help)

Focus:	Maintenance / Operation
Structures:	Abstract / Concrete

Ancestry:

0x000	pkt	CmdConfirm
0x028	str	CmdHeader cmd_hdr
0x028	bf	Hdr0 hdr0

Definition:

Alignment:	2-byte boundary
APID:	720/0x2D0
Attribute(s):
C type:	unsigned short
Length:	16 bits (2 bytes)
Offset:	0x028

Description:

Bitfields for the bytes 0-1 of a standard CCSDS telecommand header

Layout: (hide detail; help)

Start	Stop	Size		Item Type and Name
0	2	3		Version ver
3	3	1		isCmd isCmd
4	4	1		Sec_hdr sec_hdr
5	15	11		Apid apid

Hdr0 (bf)
|  Version ver (0-2)
|  isCmd isCmd (3)
|  Sec_hdr sec_hdr (4)
|  Apid apid (5-15)

typedef struct _ITC_Hdr0_Bfl {

    #if ENDIANNESS_IS_BIG

    /* CCSDS version */
    unsigned short       ver:3;

    /* CCSDS command bit */
    unsigned short       isCmd:1;

    /* CCSDS secondary header flag */
    unsigned short       sec_hdr:1;

    /* CCSDS application ID */
    unsigned short       apid:11;

    #elif ENDIANNESS_IS_LITTLE

    /* CCSDS application ID */
    unsigned short       apid:11;

    /* CCSDS secondary header flag */
    unsigned short       sec_hdr:1;

    /* CCSDS command bit */
    unsigned short       isCmd:1;

    /* CCSDS version */
    unsigned short       ver:3;

    #else

    #error _FILE_ ENDIANNESS NOT DEFINED

    #endif

} __attribute__((packed)) ITC_Hdr0_Bfl;

typedef union _ITC_Hdr0 {

    /* underlying unsigned short */
    unsigned short                  us;

    /* struct mapped bitfield */
    struct _ITC_Hdr0_Bfl            bf;

} ITC_Hdr0;

Fields:

Apid (index)

Attribute(s):  

Brief:  "CCSDS application ID"

Instance(s):  apid

Standard CCSDS application identifier.

isCmd (index)

Attribute(s):  

Brief:  "CCSDS command bit"

Instance(s):  isCmd

Set for telecommands, clear for telemetry.

Sec_hdr (index)

Attribute(s):  

Brief:  "CCSDS secondary header flag"

Instance(s):  sec_hdr

Set when a CCSDS packet includes a secondary header. Clear otherwise. All LAT telemetry/telecommands carry a secondary header.

Version (index)

Attribute(s):  

Brief:  "CCSDS version"

Instance(s):  ver

Standard CCSDS version code