When the clcw is to be encoded for a particular

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Unformatted text preview: no buffer space available in which to place any further received Type-A FDUs. The state machine enters the ‘Wait’ State when it has received a Type-A FDU, but is unable to deliver it to the Higher Procedures because there is no buffer available (see 3.2.2). It leaves the ‘Wait’ State when at least one buffer becomes available for placing a Type-A FDU. ‘Lockout’ State is entered if the state machine receives a Transfer Frame with sequence number N(S) outside the range expected if FOP-1 is operating correctly. It is a safe state in that no Type-A FDUs will be accepted or transferred to the Higher Procedures when in the ‘Lockout’ State. The state machine leaves the ‘Lockout’ State upon receipt of an ‘Unlock’ Control Command. 6.1.3 LOCKOUT_FLAG The Lockout_Flag is set to ‘1’ whenever the state machine is in ‘Lockout’ State; otherwise, it is ‘0’. When the CLCW is to be encoded for a particular Virtual Channel, the value of this flag is inserted into the ‘Lockout’ Flag field of the CLCW of that Virtual Channel. 6.1.4 WAIT_FLAG The Wait_Flag is set to ‘1’ whenever the state machine is in ‘Wait’ State; otherwise, it is ‘0’. When the CLCW is to be encoded for a particular Virtual Channel, the value of this flag is inserted into the ‘Wait’ Flag field of the CLCW of that Virtual Channel. 6.1.5 RETRANSMIT_FLAG The Retransmit_Flag is set to ‘1’ whenever the state machine knows that a Type-AD Transfer Frame has been lost in transmission or has been discarded because there was no buffer space available; otherwise, it is ‘0’. When the CLCW is to be encoded for a particular Virtual Channel, the value of this flag is inserted into the ‘Retransmit’ Flag field of the CLCW of that Virtual Channel. At the sending end, the ‘set’ condition of this flag forms a negative acknowledgement of all previously transmitted Transfer Frames with N(S) equal to or greater than N(R). The flag will be reset to ‘0’ upon successful receipt...
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This document was uploaded on 03/06/2014.

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