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9-51
9 Troubleshooting and Maintenance
CJ-series Serial Communications Units Operation Manual for NJ-series CPU Unit(W494)
9-5 Even
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9-5-3 Error De
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Event name Overrun Error, Framing Error, or Parity Error (Transmis-
sion Error) Event code 846C 0000 hex
Meaning An overrun error, framing error, or parity error occurred.
Source PLC Function Module Source details CJ-series Unit Detection
timing During Modbus-
RTU Slave Mode
Error attributes Level Observation Recovery --- Log category System
Effects User program Continues. Operation Not affected.
System-defined
variables Variable Data type Name
None --- ---
Cause and
correction Assumed cause Correction Prevention
The communications conditions and
baud rate settings do not match the
host. Review the system settings, host set-
tings, and programming, including the
command format and response for-
mat, based on *_P1_TransErrSta and
*_P2_TransErrSta (Transmission
Error Status). Perform countermeasures in
advance.
Noise or other external interference. • Use shielded twisted-pair cables for
the communications cables.
• Wire the communications cables in
separate ducts from power lines.
• Check the environment for noise.
• If required, perform retry processing
for communications.
The baud rate is outside the allowable
range or there are bit errors due to dif-
ferent stop bit settings or other
parameters. • Review the system settings.
• Review the baud rate and other
host settings, and the programming,
including the command format and
response format.
• The communications cable wiring is
faulty.
• Terminating resistance is not set
correctly for the RS-422A/485 ports.
• Wiring is faulty or terminating resis-
tance is not set correctly on an NT-
AL001 or other Adapter.
• Check the communications cable
connections.
• Turn ON the terminating resistance
(with the terminating resistance
ON/OFF switch) at both ends (at
the host).
Attached
information Attached information 1: Port number where error was detected
Precautions/
Remarks You can check the number of transmission errors (i.e., overrun errors, framing errors, and parity errors) in the
*_P1_MbsTxErrCnt and *_P2_MbsTxErrCnt device variables.