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These Frames use the Sequence-Controlled (or
AD) Service of the COP. 0 1 Reserved for future application. 1 0 Type-BD. Frame Data Field carries TC data
(e.g., Packets or Segments), with all frame
acceptance checks bypassed under control of
the FARM. These Frames use the Expedited
(or BD) Service of the COP. 1 1 Type-BC. Frame Data Field carries FARM
Control Commands, with all frame acceptance
checks bypassed under control of the FARM.
These Frames control the SequenceControlled Service of the COP. (4) RESERVED SPARES (Bits 4,5)
These two bits are reserved for future application. At present, Bits 4,5 shall be set
to value “00”. (5) SPACECRAFT IDENTIFIER (Bits 6 through 15)
These ten bits carry the identification code for the spacecraft being commanded.
The Secretariat of the CCSDS assigns the SPACECRAFT IDENTIFIER to each
vehicle within a particular mission as defined in Reference . CCSDS 202.0-B-2 Page 4-5 CCSDS HISTORICAL DOCUMENT November 1992 CCSDS HISTORICAL DOCUMENT
CCSDS RECOMMENDATION FOR TELECOMMAND: DATA ROUTING SERVICE The third and fourth octets of the FRAME HEADER contain the following field allocations:
(6) VIRTUAL CHANNEL IDENTIFIER (Bits 16 through 21)
As described in Section 3, the Transfer layer provides a “Virtual Channel” service
to the Segmentation layer. Beneath the Transfer layer is the single physical
telecommand data channel which is provided by the Channel Service (Reference
). The Virtual Channel facility allows this single physical channel to be
logically multiplexed, on a frame-by-frame basis, so that its transmission capacity
may be shared.
Every TC Transfer Frame shall have a 6-bit VIRTUAL CHANNEL ID field
present in the Frame Header. Each state of the identifier creates one Virtual
Channel, from VC 0 to VC 63, so that up to 64 different logical paths may be
defined through the single physical channel. The Transfer layer may therefore
present up to 64 Virtual Channels to the Segmentation layer.
Each Virtual Channel may also have up to 64 Multiplexer Access Poin...
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