Mitsubishi Electric FX3U-ENET User Manual page 102

5 COMMUNICATION PROCEDURE
Open request signal
PLC
(CLOSE processing
Ethernet
module
Ethernet
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POINT
This example uses connection number 1 for explanation. Use the corresponding
BFM No. and bits for other connection numbers.
*1 Processing when the open processing is abnormally completed
(TCP)
When opening from the Ethernet module under a normal situation,
if the Ethernet module sends a SYN, the external device returns
an ACK and a SYN.
However, if the Ethernet module sends a SYN and then the
external device returns a RST, the open abnormal completion
(BFM#28 b6) is immediately turned on and open processing ends.
*2 The open status and error code at abnormal end can be confirmed
with the following buffer memory.
• Each connection open abnormal code area of the
communication status storage area
(Connection numbers 1 to 8; BFM#120 to 199)
• Error log area (BFM#227 to 372)
• Error codes stored in the open error code area are cleared when
writing "0001
operation.
*3 Processing when the close processing is abnormally completed
(TCP) When closing normally from the Ethernet module, the
Ethernet module sends a FIN request and the external device
returns an ACK and a FIN. However, if an ACK and a FIN are not
returned because the external device is faulty, the Ethernet
module forcibly disconnects the connection (sends a RST
message).
1)
execution)
Open completion
signal
Close abnormal processing
FIN
" to the BFM #1602 to 1609 to perform the open
H
2)
FIN is not sent after waiting for the TCP
end timer
3)
At normal completion
FIN
4)
ACK
MELSEC-F
5) 7)
6)
RST
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