27 TROUBLESHOOTING
27.3 Troubleshooting by Symptom
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27
27.3 Troubleshooting by Symptom
The troubleshooting for any troubles generated during communication between C24 and the target device by trouble symptom
are as shown below.
When any trouble occurs, check on the C24 condition at first, and check the relevant item in the table below.
*1 For details on LED status, refer to the following manual.
MELSEC iQ-R Serial Communication Module User's Manual (Startup)
*2 For details on how to check the hardware information communication error, refer to the following section.
Page 441 Checking error status
*3 If an error occurs while performing data communication using the modem function, first check the following items and determine whether
or not the error is caused by the modem/TA connection.
If an error relating to the modem function occurs, take corrective actions according to the following items shown below:
Check of the ON/OFF status of current input/output signals on C24
Check of the error code storage status for the modem function
Check of the ON/OFF status of the DR terminal on the modem/TA (Refer to the instruction manual for modem/TA.)
Symptom Symptom description Protocol
MC Nonpro
cedural
Bidirec
tional
Predefi
ned
LED turns ON or flashes
*1
Page 459 SD LED does not flash even after a send request was
made
Page 459 RD LED does not flash even though the target device is
transmitting a message
Page 460 No response message is returned even though the
target device transmitted a message and the RD LED flashes
Page 461 Read request signal does not turn ON even though the
target device transmitted a message and the RD LED flashes
Page 462 The CPRTCL instruction execution is not completed
although the RD LED flashes
Page 463 RUN LED turns OFF
Page 463 ERR LED flashes
Page 464 ERR LED turns ON
Page 465 C ERR LED turns ON
Communication error occurred Page 466 Hardware information communication error "SIO"
occurs
*2
Page 467 Hardware information communication error "PRO."
occurs
*2
Page 468 Hardware information communication error "P/S"
occurs
*2
Page 468 Hardware information communication error "C/N"
occurs
*2
Page 469 Hardware information communication error "NAK"
occurs
*2
Page 469 Communication is intermittent
Page 470 Undecodable data are transmitted or received
Page 471 Whether the communication error is caused on C24 or
target device is unclear
Communication via modem cannot
be established
*3
Page 471 Communication is not established via modem
Page 472 Communication is not established with the ISDN sub-
address when using a modem
The programmable controller CPU
monitoring function does not operate
in the specified cycle
Page 472 Fixed cycle send is not performed normally
Page 472 Condition match send is not performed normally
Data cannot be received by an
interrupt program
Page 472 Data cannot be received by an interrupt program
The initial setting cannot be
configured
Page 472 Data cannot be written to flash ROM
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