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Responding to Displayed Error Messages Section 7-2
• Overrun error
• FCS (sum value) error
• Time out error
• Data over flow error
• PLC unit No. error (Host Link only)
• NAK received (in the case of the Host Link, the end code is also dis-
played)
• Undefined command error
Send Errors
The following errors can occur when receiving data.
• Time out error
• Data over flow error
Probable Causes and
Remedies
The remedies to take in accordance with the displayed cause are indicated in
the table below.
Error Details Displayed Probable Cause Remedy
Parity Error
Framing Error
Over-run Error
Communications parameters/
conditions set incorrectly.
Check if the settings at the host for parity bit, frame
length, communications speed, stop bit length and
flow control agree with those at the NT631/NT631C.
The connecting cables are not con-
nected correctly.
Check the communications cable connection and
perform a conductivity test. If there is a fault, replace
the cable. For details on communications cables,
refer to SECTION 4 Connecting to the Host from the
RS-232C Port, and SECTION 5 Connecting to the
Host from the RS-422A/485 Port.
Noise caused data corruption during
communications.
Carry out grounding work in accordance with the
conditions by referring to 3-1-4 Grounding, page 34.
FCS (Check Sum) Error Noise caused data corruption during
communications.
Carry out grounding work in accordance with the
conditions by referring to 3-1-4 Grounding, page 34.
The PLC is transmitting incorrect
data.
Check the operation at the host side.
Time-out Error The connecting cables are not con-
nected correctly. (Send/Receive)
Check the communications cable connection and
perform a conductivity test. If there is a fault, replace
the cable. For details on communications cables,
refer to SECTION 4 Connecting to the Host from the
RS-232C Port, and SECTION 5 Connecting to the
Host from the RS-422A/485 Port.
The communications service of the
host is stopped. (Send/Receive)
Check that the host is capable of communicating with
the NT631/NT631C (confirm that the communica-
tions settings of the host and NT631/NT631C match).
Time-out Interval is too short. (Send) Set a longer value for Time-out Interval at the host
side.
Time-out Interval is too short.
(Receive)
Set a longer value for Time-out Interval in the System
Menu. (6-9-12 Setting the Time-out Interval,
page 181) It may also be possible to solve the prob-
lem by shortening the host cycle time.
PLC Unit No. Error The unit # does not match that set on
the PLC.
Re-set the unit number at the host side to 0.
Noise caused data corruption during
communications.
Carry out grounding work in accordance with the
conditions by referring to 3-1-4 Grounding, page 34.