12762 if the synchronization flag is set to 0 the

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Unformatted text preview: 4.1.2.7.6.3 The locations of the octets in the Transfer Frame Data Field shall be numbered in ascending order. The first octet in this Field is assigned the number 0. The First Header Pointer shall contain the binary representation of the location of the first octet of the first Packet that starts in the Transfer Frame Data Field. NOTES 1 The purpose of the First Header Pointer is to facilitate delimiting of variable-length Packets contained within the Transfer Frame Data Field by pointing directly to the location of the first Packet from which its length may be determined. 2 The locations of any subsequent Packets within the same Transfer Frame Data Field will be determined by calculating the locations using the length field of these Packets. CCSDS 132.0-B-1 Page 4-7 September 2003 CCSDS RECOMMENDATION FOR TM SPACE DATA LINK PROTOCOL 3 If the last Packet in the Transfer Frame Data Field of Transfer Frame N spills over into Frame M of the same Virtual Channel (N<M), the First Header Pointer in Frame M ignores the residue of the split Packet and indicates the start of the next Packet that starts in Frame M. 4.1.2.7.6.4 If no Packet starts in the Transfer Frame Data Field, the First Header Pointer shall be set to ‘11111111111’. NOTE – The above situation may occur if a long Packet extends across more than one Transfer Frame. 4.1.2.7.6.5 If a Transfer Frame contains only Idle Data in its Transfer Frame Data Field, the First Header Pointer shall be set to ‘11111111110’. NOTE – A Transfer Frame with its First Header Pointer set to ‘11111111110’ is called an OID Transfer Frame, meaning that it has Only Idle Data in its Data Field (see 4.1.4.6). 4.1.3 TRANSFER FRAME SECONDARY HEADER 4.1.3.1 General 4.1.3.1.1 If present, the Transfer Frame Secondary Header shall follow, without gap, the Transfer Frame Primary Header. 4.1.3.1.2 The Transfer Frame Secondary Header is optional; its presence or absence shall be signaled by the Transfer Frame Secondary Header Flag...
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