Mitsubishi Melsec-L Series User Manual page 304

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REMARKS
The following are precautionary notes when exchanging data with an external device
via one of the C24 interfaces.
(1) When the power supply to the C24 or external device is started, the remote
device that is connected may generate a reception error.
(2) If the remote device that is connected starts up while data is being transmitted,
the remote device side will generate a reception error.
(3) When the C24 error LED turns on because a reception error has occurred, turn
off the light if necessary in accordance with Section 15.4.
Also, if a reception error has occurred on the external device side, handle the
error by seeing to the operating manual for the external device.
Handle the occurrence of a reception error on the C24 side using the
following corrective actions.
• When communicating with the MC protocol
The C24 will disregard the received data or returns a response message
indicating an abnormal termination if it detects a reception error after
receiving the head data of the command message in the set format. If the
reception error is detected before the head data of the command message
in the set format is received, the received data will be disregarded.
• When communicating using nonprocedural protocol
If the C24 detects a reception error, the reception abnormal detection
(X4/XB) turns ON.
Perform procedures such as detection of reception error or clearing
received data as required by following the explanations found in Sections
10.1.4 and 10.1.5.
• When communicating using bidirectional protocol
When the C24 detects a reception error after the head data of a
communication message for bidirectional protocol is received, it returns a
response message indicating an abnormal termination.
If the reception error is detected before the head data of the
communication message for bidirectional protocol is received, the
received data will be disregarded.
• When communicating using the predefined protocol
If a reception error occurs, an error code is stored in the Data reception
result area (address: 258
Reception error codes can be also checked with the communication data
monitoring function.
Take actions such as detecting a reception error or clearing the received
data, if necessary.
For details of the communication data monitoring function, refer to the
User's Manual (Application).
/268 ) of the C24.
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15 TROUBLESHOOTING
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