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MELSEC-F
COMMUNICATION PROCEDURE5
5 - 33
5.6.2 Passive open processing/close processing
This section explains the procedure for opening and closing a connection with the
Ethernet module via an external device.
The operations of Passive open processing/close processing differ depending on
whether "Always wait for OPEN" or "Do not wait for OPEN" is selected, as shown in
this section.
(1) When "Always wait for OPEN" is selected in the operational setting
This is an explanation of (BFM #24 b8: ON) open processing/close processing
when initial timing settings for Operational Settings are set to be always wait
OPEN (Communication Possible at STOP).
In this case, sequence programs for open processing and close processing are
not required because the Ethernet module keeps the connection in the always
wait for the OPEN status according to the [Open settings] parameter setting.
For detail on the [Open settings] parameter, see Section 5.5, "Open Settings".
*1 An open request (SYN) received after the normal completion of an
initial processing and before the Ethernet module is placed in the
open acknowledge enabled status generates an error, and the
Ethernet module sends a connection forced close (RST).
Open status
Open allowed status(Listen status)
(Active open acknowledge
enabled)
Close status
Initial normal completion
BFM#27="0001
H"
Open completion signal
BFM#20480
Power-on
Parameter
communication
completed
1)
2)
FIN
3)
SYN + ACK FIN + ACK
Open allowed status
BFM#20482
SYN
4)
(*1)