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MELSEC-Q
10 TROUBLESHOOTING
10.3.8 Troubleshooting when communication error "PRO." generates
Symptom Cause Corrective action MC
Bidirectional
Non
procedure
• Communications were
performed with a control
procedure different from
the Q series C24
communication protocol
setting.
• Some of the data are
different from the control
procedure.
• Designated command
does not exist.
• The device No.
designation is not the
character count
corresponding to the
command.
• Check the Q series C24 communication
protocol setting and the message from the
external device and match the settings, or
correct the message and restart data
communications.
• The characters in the
message include a data
other than the "A to Z",
"0 to 9", "
", and
control data.
• Check and correct the external device message
and restart data communications.
Note
• Only the data "0 to 9" and "A to F" can be
handled as character area data during
communications using an MC protocol (ASCII
mode). Therefore, when transmitting a
character string as data, convert the ASCII code
of each character string to 2-byte binary code.
Examples)
• Transmitting the character "G"
The ASCII code for the character "G" is 47
H
and is transmitted as the two bytes 34
H
, 37
H
.
• Transmitting the character "A"
The ASCII code for "A" is 41
H
and is
transmitted as the two bytes 34
H
, 31
H
.
If the ASCII code 41
H
for the character "A" is
transmitted unchanged, the Q series C24
ASCII-BIN conversion will convert it to A
H
(10) and pass it to the PLC CPU.
• A device No. outside the
designated range was
designated.
• When designating a device, check "Device
setting" of the parameters written to the CPU
and correct it to a device No. within the
designated range and restart data
communications.
• Communication error
signal "PRO" turned on.
• A remote RUN/STOP
request was issued
while remote STOP was
applied from another
module.
• Check if remote STOP is applied from another
module and restart data communications.
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