C third case ns vr and ns vr nw the transfer

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Unformatted text preview: Frame, go into the ‘Lockout’ State and set the ‘Lockout’ Flag. When N(S) falls inside the FARM Sliding Window, one of the following three cases will occur: a) First case: N(S) = V(R) The Transfer Frame is in the Positive Window and contains the expected Frame Sequence Number; the Transfer Frame is accepted. This is the case when COP-1 is operating correctly and no previous Transfer Frames have been lost or discarded. It is also the case when retransmitted Transfer Frames are received after they have been lost or discarded. b) Second case: N(S) > V(R) and N(S) ≤ V(R) + PW – 1 CCSDS 232.1-B-2 Page 6-5 September 2010 RECOMMENDED STANDARD FOR COMMUNICATIONS OPERATION PROCEDURE-1 The Transfer Frame is in the Positive Window and does not contain the expected Frame Sequence Number; the Transfer Frame is discarded and the Retransmit_Flag is set, if it has not already been set. This case occurs when a previous Transfer Frame has been lost or discarded and retransmission has not yet started. c) Third case: N(S) < V(R) and N(S) ≥ V(R) - NW The Transfer Frame is in the Negative Window and is discarded without any other action being taken. This case occurs if Transfer Frames are retransmitted even though they have been accepted. This could happen, for example, if the FOP T1_Initial has been set to a too-small value or if there is a link outage. It may occur during operations using the forced-retransmission mechanism for deep space missions. Certain missions may require only a single transmission of a sequence of Type-AD Transfer Frames in one COP-1 session (Transmission_Limit = 1), whether in the Suspend/Resume mode of operation or not. For such missions and in such a mode, it is permitted to set PW > NW, with, ultimately, NW = 0 and PW = W, where ‘W’ can be any integer between 1 and 256 inclusive. Thus: PW ≤ W and 1 ≤ W ≤ 256 and 1 ≤ PW ≤ 256 Whatever the value of PW, the value of the FOP_Sliding_Window_Width (K) may never exceed 255. 6.2 6.2.1 FARM-1 ACTIONS GENERAL This section defines the actions used in the FARM-1 State Table...
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This document was uploaded on 03/06/2014.

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