The frame acceptance and reporting mechanism farm

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Unformatted text preview: the BYPASS FLAG. The Frame Acceptance and Reporting Mechanism (FARM) associated with the COP can be made to operate in a normal “Acceptance” (frame “Type-A”) mode or a “Bypass” (frame “Type-B”) mode, according to the setting of the BYPASS FLAG. Setting Bit 2 to value “0” specifies a Type-A TC Frame; acceptance of this Type of frame by the spacecraft shall be subject to the normal frame acceptance checks of the FARM. Setting Bit 2 to value “1” specifies a Type-B TC Frame; the normal frame acceptance checks of the FARM shall be bypassed. Necessarily, it must be possible to send Type-A and Type-B TC Frames on the same TC Virtual Channel in order to conduct some operations. (3) CONTROL COMMAND FLAG (Bit 3) The CONTROL COMMAND FLAG specifies whether the data field of the TC Transfer Frame is conveying transfer “ Control Commands” (the “C” mode), or “Data” (the “D” mode). In the “C” mode the Frame Data Field contains control information which is used to set the parameters of the FARM to the proper configuration to accept telecommand data. In the “D” mode the Frame Data Field contains a Frame Data Unit (e.g., a TC Packet or a TC Segment). Setting Bit 3 to value “0” indicates the “D” mode to the receiving spacecraft, i.e., that the Frame Data Field contains data. CCSDS 202.0-B-2 Page 4-4 CCSDS HISTORICAL DOCUMENT November 1992 CCSDS HISTORICAL DOCUMENT CCSDS RECOMMENDATION FOR TELECOMMAND: DATA ROUTING SERVICE Setting Bit 3 to value “1” indicates the “C” mode to the receiving spacecraft, i.e., that the Frame Data Field contains Control Commands. The combined states of the BYPASS FLAG and the CONTROL COMMAND FLAG are interpreted by the receiving spacecraft as shown in Table 4-1. Table 4-1: Interpretation of the “Bypass” and “Control Command” Flags Bypass Flag Control Command Flag Interpretation 0 0 Type-AD. Frame Data Field carries TC data (e.g., Packets or Segments), subject to acceptance check under control of the FARM...
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This document was uploaded on 03/06/2014.

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