Mitsubishi MELSEC LJ71C24, User Manual

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15 TROUBLESHOOTING
15.3 Troubleshooting by Symptom
This following shows troubleshooting of trouble generated during communications
between the C24 and external device according to the trouble symptom.
When trouble occurs, first confirm the status of the C24 and check the relevant item in
the table below.
Protocol
Symptom Symptom description
Dedicated
Non-
proce-
dural
Bi-
direc-
tional
Pre-
defined
Reference
•
"RUN" LED turned off. Section 15.3.1
•
"RD" does not blink even through an external device
is transmitting a message.
Section 15.3.2
•
An external device transmitted a message and "RD"
blinked, but the C24 did not return a response
message. Section 15.3.3
•
"SD" does not blink even after a send request was
made.
Section 15.3.4
•
An external device transmitted a message and "RD"
blinked, but the C24 did not turn ON the read
request. Section 15.3.5
•
The CPRTCL instruction is not completed even
though "RD" was blinking.
Section 15.3.6
LED turns on/off (check according to
Chapter 2)
•
"ERR." LED turns on. Section 15.3.23
•
The "NAK" was turned ON. Section 15.3.7
•
The "C/N" was turned ON. Section 15.3.8
•
The "P/S" was turned ON. Section 15.3.9
•
The "PRO." was turned ON. Section 15.3.10
•
The "SIO" was turned ON. Section 15.3.11
•
The "CH1 ERR." or "CH2 ERR." was turned ON. Section 15.3.12
•
Communications are intermittently established and
lost.
Section 15.3.13
•
Data that cannot be decoded was transmitted and
received.
Section 15.3.14
Communication errors occurred
(check according to Section 15.2.1)
•
Whether the cause of the communications error is in
the C24 or the external device is unknown.
Section 15.3.15
•
Cannot communicate via modem. Section 15.3.16 Cannot communicate via modem
(
1
)
•
Cannot communicate with ISDN sub-address. Section 15.3.17
•
Does not operate in the cycle time designated in the
constant cycle transmission setting.
Section 15.3.18 The programmable controller CPU
monitoring function does not operate
in the designated cycle time.
•
Does not operate in the cycle time designated in
condition agreement transmission setting.
Section 15.3.19
Cannot receive by an interrupt
program
•
Cannot receive data. Section 15.3.20
Cannot perform initial setting
•
Cannot write setting value in flash ROM of the C24. Section 15.3.21
1 If an error occurs while performing data exchange using the modem function
described in User's Manual (Application), 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 C24.
• Check the storage status for error codes related to the modem function.
• Check the ON/OFF status of the DR terminal of the modem/TA. (Refer to the
manual for the modem/TA.)