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27 TROUBLESHOOTING
27.3 Troubleshooting by Symptom
The CPRTCL instruction execution is not completed although the
RD LED flashes
Symptom Cause Corrective action MC Non Bi Pd
When the CPRTCL
instruction was executed for
the protocol with the
communication type set to
"Receive Only" or "Send &
Receive", RD LED flashes,
but the instruction execution
is not completed.
Incorrect protocol number is
specified in the control data.
• Review the protocol number specified in the control data for
the CPRTCL instruction.
The CD terminal has been
turned OFF when the CD
terminal check is enabled.
• Change the wiring so that the CD terminal remains ON all
the time since a message is skipped if the CD terminal is
OFF when the CD terminal check is set to be enabled.
The user-edited protocol
setting with the Predefined
protocol support function of
Engineering tool is
inconsistent with the packet
format of the target device.
Check the packet format of the target device, and review the
protocol setting.
• In the packet setting, are the element type and element
order incorrect?
• Is each element setting item (Code type, Data length, Data
flow, Calculating range, etc.) incorrect?
C24 has not received the
expected packet.
Check the data transmitted from the target device with the
Circuit Trace function of Engineering tool, and correct the
message if it's incorrect.
When proper data are being transmitted from the target
device, take the corrective action by referring to the
troubleshooting below.
• Page 463 ERR LED flashes
• Page 469 Communication is intermittent
C24 has cleared the data
received before the protocol
execution. (On the "Protocol
Detailed Setting" screen of
Engineering tool predefined
protocol support function,
"Clear receive data before
protocol execution" is
designated.)
• When data may be received before protocol execution,
unselect the checkbox for "Clear OS area (receive data
area) before protocol execution" on the "Protocol Detailed
Setting" screen of Engineering tool predefined protocol
support function.
The C24 data
communications monitoring
time is set to "Unlimited wait",
or the monitoring time is too
long.
• Perform cancel processing to complete the CPRTCL
instruction execution.
• Set or shorten the monitoring time and retransmit the
message from the external device and determine the trouble
from the contents of the time-out error.
■Remarks
In the cases below, errors can be detected by setting the
receive wait time for the "Receive Setting" on the "Protocol
Detailed Setting" screen of Engineering tool predefined
protocol support function.
• When part of a message is skipped.
• When transmission from the target device is interrupted.
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