Whether The Communication Error Is Caused On The Q Series C24 Or External Device Is Unclear - Mitsubishi Electric QJ71C24N User Manual

11 TROUBLESHOOTING
11.3.15 Whether the communication error is caused on the Q series C24 or external device
is unclear.
Symptom
• Whether the
communications error
cause is in the Q
series C24 or an
external device is
unclear.
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Cause
• Test the Q series C24 as described below to
check where the cause is.
1) Check the hardware.
• The Q series C24 must be installed
firmly.
• The pins of the Q series C24 must not
be bent or otherwise abnormal.
2) Test the Q series C24 alone. (See Section
4.7.)
• ROM/RAM/switch test must not
generate any errors.
• Self-loopback test must not generate
any errors.
3) Check the state of the programmable
controller CPU.
• There must not be any errors that stop
programmable controller CPU
operation.
Note
• The following methods are available for

testing if normal communications are
possible with the Q series C24 alone.
1) With one the Q series C24, set CH1 and
CH2 to the non procedure protocol and
connect the wiring the same as for the
self-loopback test and transmit data
from one channel and receive the
transmitted data at the other channel. If
the transmitted data and the received
data are the same, transmit and receive
processing is performed normally.
2) When two Q series C24 are available,
set one Q series C24 to the non
procedure protocol and the other Q
series C24 to the MC protocol and
transmit an MC protocol message from
the non procedure protocol station. If the
MC protocol station returns the transmit
message normally, transmit and receive
processing is normal.
Corrective action
MELSEC-Q
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