Troubleshooting By Symptom - Mitsubishi QJ71C24/-R2 User Manual

10 TROUBLESHOOTING

10.3 Troubleshooting by Symptom

Symptom
LED turns on/off (check according to
Section 4.3)
Communication errors occurred
(check according to Section 10.1.1)
Cannot communicate via modem
1
)
(
The PLC CPU monitoring function
does not operate in the designated
cycle time.
Cannot receive by an interrupt
program
Cannot perform initial setting
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This following shows troubleshooting of trouble generated during communications
between the Q series C24 and external device according to the trouble symptom.
When trouble occurs, first confirm the status of the Q series C24 and check the
relevant item in the table below.
Symptom description
"RUN" LED turned off.
"RD" does not blink even through an external device
is transmitting a message.
An external device transmitted a message and "RD"
blinked, but the Q series C24 did not return a
response message.
An external device transmitted a message and "RD"
blinked, but the Q series C24 did not turn ON the
read request.
ERR. LED turns on.
The "NAK" was turned ON.
The "C/N" was turned ON.
The "P/S" was turned ON.
The "PRO" was turned ON.
The "SIO" was turned ON.
The "CH1. ERR. " or "CH2. ERR. " was turned ON.
Communications are intermittently established and
lost.
Data that cannot be decoded was transmitted and
received.
Whether the cause of the communications error is in
the Q series C24 or the external device is unknown.
Cannot communicate via modem.
Cannot communicate with ISDN sub-address.
Does not operate in the cycle time designated in the
constant cycle transmission setting.
Does not operate in the cycle time designated in
condition agreement transmission setting.
Cannot receive data.
Cannot write setting value in flash ROM of the Q
series C24.
1 If an error occurs while performing data exchange using the modem function
described in User's Manual (Application) Chapter 3, first check the following items
and confirm whether or not the error is caused by the modem/TA connection.
If an error relating to the modem function is occurring, perform necessary
corrective actions for each cause according to the reference sections given below:
• Check the ON/OFF status of current I/O signals of the Q series C24.
• Check the storage status for error codes related to the modem function. (See
Sections 10.2.3.)
• Check the ON/OFF status of the DR terminal of the modem/TA. (See the
manual for the modem/TA.)
Protocol
Non Bidirec-
Dedicated
procedure tional
MELSEC-Q
Reference section
Section 10.3.1
Section 10.3.2
Section 10.3.3
Section 10.3.4
Section 10.3.20
Section 10.3.5
Section 10.3.6
Section 10.3.7
Section 10.3.8
Section 10.3.9
Section 10.3.10
Section 10.3.11
Section 10.3.12
Section 10.3.13
Section 10.3.14
Section 10.3.15
Section 10.3.16
Section 10.3.17
Section 10.3.17
Section 10.3.19
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