Omron NT31C Reference Manual page 428

Responding to Displayed Error Messages
Probable Causes and
Remedies
Error Details
Parity Error
Framing Error
Over-run Error Over-run Error
FCS (Check Sum) Error
Time-out Error
PC Unit No. Error
NAK received
Undefined Command
Error E
420
The remedies to take in accordance with the displayed cause are indicated in the
table below.
Displayed Probable Cause
Communication parameters/
conditions set incorrectly.
The connecting cables are not
connected correctly.
Noise caused data corruption during
communication.
Noise caused data corruption during
communication.
The PC is transmitting incorrect
data.
The connecting cables are not
connected correctly. (Send/Receive)
The communication service of the
host is stopped. (Send/Receive)
Time-out Interval is too short. (Send)
Time-out Interval is too short.
(Receive)
The unit # does not match that set
on the PC.
Noise caused data corruption during
communication.
——
The host is not supported.
Instruction level 3 is not effective.
Remedy
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 PT.
Check the communication cable connection and
perform a conductivity test. If there is a fault,
replace the cable. For details on communication
cables, refer to Connecting to the Host from the
RS-232C Port in section 4 or Connecting to the
Host from the RS-422A/485 Port in section 5 in the
Setup Manual .
Carry out grounding work in accordance with the
conditions. (Refer to Grounding in section 3 in the
Setup Manual .)
Carry out grounding work in accordance with the
conditions. (Refer to Grounding in section 3 in the
Setup Manual .)
Check the operation at the host side.
Check the communication cable connection and
perform a conductivity test. If there is a fault,
replace the cable.
For details on communication cables, refer to
Connecting to the Host from the RS-232C Port in
section 4 or Connecting to the Host from the
RS-422A/485 Port in section 5 in the Setup Manual .
Check that the host is capable of communicating
with the PT (confirm that the communication
settings of the host and PT match).
Set a longer value for Time-out Interval at the host
side.
Set a longer value for Time-out Interval in the
System Menu. (Refer to Setting the Time-out
Interval in section 6 in the Setup Manual .) It may
also be possible to solve the problem by shortening
the host cycle time.
Re-set the unit number at the host side to 0.
Carry out grounding work in accordance with the
conditions. (Refer to Grounding in section 3 in the
Setup Manual .)
Check the settings for allocated words and bits.
If noise is a possible factor, distance the cable from
sources of noise and insert a noise filter in the
power supply line.
If using the equipment in a location subject to a lot
of noise, use a cable with a high degree of
protection against noise for the transmission route.
Also make the cable as short as possible.
Check the PC model used for the host.
Check that the instruction level setting for the host is
level 1, 2, 3.
Section 6-2