MA28140 Datasheet, PDF (11/72 Pages) Dynex Semiconductor – Packet Telecommand Decoder

MA28140
POSITIVE WINDOW AREA = PW
N(S)=V(R)+PW-1
DISCARD FRAME &
SET RETRANSMIT
DISCARD
FLAG
N(S)=V(^ARC)+C1EPT
FRAME &
SET V(R)=V(R)+1
FRAME & GO TO
LOCKOUT
N(S)=V(R)-1
STATE
N(S)=V(R)
DISCARD FRAME
N(S)=V(R)-NW
NEGATIVE WINDOW AREA = NW
Figure 5: The FARM Sliding Window Concept
A Frame Sequence Number N(S) falls outside the FARM Sliding Window i.e. in the Lockout Area when:
N(S)>V(R)+PW-1
N(S)<V(R)-NW
In this case, the Lockout flag is set.
When N(S) falls inside the FARM Sliding Window, one of the following three cases can occur:
• First case
N(S)=V(R)
The frame is accepted
• Second Case
N(S)>V(R) and
N(S)≤V(R)+PW-1
The frame is in the positive window and does not contain the expected Frame Sequence Number. The Frame is discarded
and the retransmit Flag is set.
• Third Case
N(S)<V(R) and
N(S)≥V(R)-NW
The frame is in the negative window and is discarded without any other action being taken.
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