Mitsubishi MELSEC-F User Manual page 258

11 TROUBLESHOOTING
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(b) If the data length specified immediately after the subheader is larger than
the amount of text data received
1) The Ethernet module waits for the reception of the remaining missing
data.
2) If the remaining data could be received within the time allotted by the
response monitoring timer, the Ethernet module performs processing
according to the code in the subheader.
3) If the remaining data could not be received within the time allotted by
the response monitoring timer, the Ethernet module performs the
following processing.
• Sends the ABORT (RST) instruction to the external device and
closes the line.
• Notifies the PLC side about occurrence of an open error via the
open error detection signal (BFM#28.b6=ON)
• Stores the error code in the open error code storage area. (The
error code is not stored in the error log storage area.)
POINT
Designate the actual data size of the text field for "data length" specified in the
application data field of a message sent from the external device to the Ethernet
module.
The Ethernet module never sends text whose size is different from the specified
data length to the external device.
(2) When communication is performed using fixed buffer (non-procedure)
Since no message data length is specified in non-procedure communication,
the data received is stored in the receive buffer area as is.
It is recommended to set up some method of checking that the data is received
correctly. This can be achieved for instance by including the data length and
data type code in the application data of the message, so that the number of
bytes and type of application data can be identified on the receiving side.
MELSEC-F
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