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MELSEC-Q
10 TROUBLESHOOTING
Protocol
Error code
(Hexa-
decimal)
Error
Error Contents
Signal
name
Corrective action
MC
Non
Proce-
dure
Bidire-
ctional
7F24
H
Sum check error
• The sum check calculated by the Q series C24 and
the received sum check are not the same.
P/S
• Recheck the external device
sum check.
7F25 H Data length error
• The length of the received data exceeds the receive
area size.
CHn
ERR.
• Correct the "data length" that is
transmitted from the external
device.
• Change the "word/byte units"
set by the Q series C24 to byte
units.
• Increase the receiving area of
the Q series C24.
7F26 H Command error
• Another command was received before an unlock
processing while the remote password is registered.
CHn
ERR.
• Perform the communication
after the unlock processing is
normally completed.
7F30H System error • The OS of the Q series C24 detected some error. — ( 1)
7F31H
Simultaneous
transmission error
• The Q series C24 and an external device started
transmitting simultaneously.
• Process by agreement with the
external device.
• When necessary, change the
simultaneous transmission data
valid/invalid designation setting
by GX Configurator-SC. (buffer
memory addresses 9B
H
/13B
H
)
7F32H System error • The OS of the Q series C24 detected some error. — ( 1)
7F40
H
• No reception watchdog timer (timer 0) time-out
occurred.
PRO
• Check if data was dropped from
the receive data.
• Check if DTR control, etc.
interrupted reception.
7F41
H
• Response watchdog timer (timer 1) time-out
occurred.
• Check the status of the
message transmission
destination and restart data
communications, as required.
7F42H
Time-out error
• Transmit watchdog timer (timer 2) time-out
occurred.
• Check if DTR control, etc.
interrupted transmission.
7F50H
to
7F54
H
7F60H
to
7F66
H
System error • The OS of the Q series C24 detected some error. — ( 1)
7F67H Overrun error
• The Q series C24 received the next data before it
completed receive processing of the previous data.
SIO
• Decrease the data transmission
rate and restart data
communications.
• Check whether a temporary stop
has occurred in the station in
which the Q series C24 is
installed. (For the QCPU this can
be checked using special register
SD1005.) If a temporary stop has
occurred, remove its cause.
7F68H Framing error
• Data does not match the stop bit setting.
• A malfunction occurred in the network because the
power source of the partner station was on or off.
• Noise occurs in the network.
• When the multidrop was connected, data was
transmitted simultaneously by multiple devices.
SIO
• Match the Q series C24 and
external device settings.
• Clear the error information
according to the error
information initialization request
(YE/YF).
In addition, when
communicating data with the
non procedure protocol, execute
the INPUT instruction, and read
and discard the unnecessary
data.
• Measure the noise.
• When connecting the multidrop,
remove the interlock so that
data will not be transmitted
simultaneously by multiple
devices.