Mitsubishi Electric MELSEC iQ-R Series User Manual page 460

Precautions
The considerations for data communication with the target device via either of C24 interfaces are shown below:
• When powering up the C24 side or the target device side, data reception error may occur at the target device side being
connected.
• When the connected target device side starts up during data transmission, the data reception error occurs at the target
device side.
• When the ERR LED on C24 turns ON due to data reception error, turn OFF the LED as necessary. (Page 448 Turning
OFF the ERR LED and initializing the error codes)
Also, when a data reception error occurs on the target device side, take corrective actions in accordance with the
instruction manuals for the target device.
■Error occurred on the C24 side
Handle the error as shown below when data reception error occurs on C24 side.
• For communications using the MC protocol
C24 will disregard the received data or return a response message indicating an abnormal completion if it detects a data
reception error after receiving the head data of the command message in the set format.
If the data 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 the predefined protocol
C24 will store the error code in the 'Data reception result' (Un\G600/616) when a data reception error occurs.
Reception error can be also checked with the send/receive data monitoring function.
Take appropriate measures such as detecting a data reception error or clearing the received data, if necessary.
For more details on the send/receive data monitoring function, refer to the following section.
(Page 387 USING SEND/RECEIVE DATA MONITORING FUNCTION)
• When communicating using nonprocedural protocol
C24 will turns ON the reception abnormal detection (X4/XB) when it detects a data reception error.
Take appropriate measures such as detecting a data reception error or clearing the received data, if necessary.
(Page 65 Reception error detection and check methods, Page 67 Receive data clear)
• For communications using bidirectional protocol
C24 will return a response message indicating an abnormal completion if it detects a data reception error after receiving the
head data of the communication message for the bidirectional protocol.
If the reception error is detected before the head data of the communication message for the bidirectional protocol is
received, the received data will be disregarded.
■Meaning of abbreviations in "Protocol" column
MC: MC protocol
Non: Nonprocedural protocol
Bi: Bidirectional protocol
Pd: Predefined protocol
27 TROUBLESHOOTING
458
27.3 Troubleshooting by Symptom