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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
7F69H Parity error
• Data does not match the parity 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.
P/S
• 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.
7F6A
H
Buffer full error
• OS receive buffer overflowed and receive data was
skipped.
SIO
• Use DTR and DC control and
perform data communications
so that the buffer does not
become full. (Perform RS ⋅ CS
control when the modem
function is used.)
• If the Read Request signal was
turned ON, execute read
immediately.
7F6B
H
CD signal control
error
• Data was received when CD signal is OFF when
"CD terminal check enabled" was designated.
CHn
ERR.
• Recheck the CD signal control
of the external device.
(Send while the CD signal is ON.)
• Set "no CD terminal checking"
and perform communication.
7F6C
H
Transmission error
• Data cannot be sent because the line is not
connected.
CHn
ERR.
• Transmit data after line
connection processing on the
interface side that uses the
modem function.
7F91
H
to
7F96
H
7F98
H
to
7F9A
H
7F9DH
7F9E
H
7FA0H
to
7FA3
H
7FA8H
7FAA
H
to
7FAD
H
7FAF
H
to
7FB2
H
7FB5
H
7FB6H
7FB8
H
to
7FBC
H
7FC0
H
to
7FC4
H
System error • The OS of the Q series C24 detected some error. — ( 1)