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Unformatted text preview: aced a ‘valid’ Transfer Frame (a Transfer Frame that has passed the Frame Validation
Check defined in reference ) into a buffer of FARM-1. However, the following operation
needs to be performed by FARM-1 before the FARM-1 State Table is applied:
verifying that a Type-BC Transfer Frame contains one of the two COP-1 control
commands (‘Unlock’ and ‘Set V(R)’).
Included in the FARM-1 State Table are the following operations:
a) checking the value of the ‘Bypass’ Flag;
b) checking the value of the ‘Control Command’ Flag;
c) checking the value of N(S) in Type-AD Transfer Frames.
220.127.116.11 Control Commands In table 6-1, Events E7 and E8 are concerned with the execution of, respectively, an ‘Unlock’
Control Command and a ‘Set V(R)’ Control Command. The specification of each action in
each box is self-explanatory. The action described for Event E8 in State (S3) means that the
‘Set V(R)’ Control Command is not executed (FARM-1 must be ‘unlocked’ first), but its
receipt is accounted for by means of the FARM-B_Counter since the control command was
validated as ‘legal’ and found ‘executable’.
NOTE – The execution of an ‘Unlock’ Control Command resets only FARM-1, not the
Higher Procedures. Some mechanism should be provided to ensure that the data
management functions of the Higher Procedures purge/reset their buffers as
required for operations of the protocol.
18.104.22.168 Buffer Release Signal If an implementation provides a scheme for flow control between FARM-1 and the Higher
Procedures and the flow control scheme ever results in the COP-1 Wait_Flag being set, the
scheme must also provide a ‘Buffer Release Signal’, which corresponds to Event E10 in the
FARM-1 State Table. In this case, FARM-1 shall be signaled when sufficient buffer space
becomes available for at least one more maximum-size Frame.
22.214.171.124 CLCW FARM-1 constantly provides some information to be sent back to FOP-1 in the CLCW
(Event E11 in the FARM-1 State Table). CCSDS 232.1-B-2 Page 6-8 September 2010 RECOMMENDED STANDARD FOR COMMUNICATIONS OPERATION PROCEDURE-1 6.3.3 FARM-1 STATE TRANSITIONS A summary of the way FARM-1 moves between states is depicted in figure 6-2.
Table 6-1: FARM-1 State Table (Part 1)
State Name WAIT LOCKOUT Main
of State Normal
to is on Lockout_
Flag is on State Number Event
Conditions OPEN S1 S2 S3 Event
V(R) A buffer is
this frame E1 Accept frame, Not
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