Communications Errors - Omron NT20 User Manual

Responding to Displayed Error Messages
7-2-6

Communications Errors

This section describes the errors relating to communications with the PLC/
Host that can occur during operation, and their remedies.
• Operation When a Communications Error Occurs
When a communications error occurs, the error message is displayed at
the NT20, and the buzzer sounds. Error messages are displayed when the
"Automatic Reset" memory switch is not set.
Some error messages are displayed even if the "Automatic Reset" memory
switch is set.
• Procedure When a Communications Error Occurs
When an error message is displayed, press the [EXIT] touch switch dis-
played on the screen. The screen display will return to the RUN mode.
• Display of Communications Errors
As shown below, communications errors are displayed in the center of the
screen, together with a classification indicating whether they are receive or
send errors.
Screen When an Error Has Occurred while Receiving
RECEIVING ERROR
EXIT
Screen When an Error Has Occurred while Sending
RECEIVING ERROR
EXIT
Message
(ACIA) Communications parameters/
conditions of communications
Parity Error
set incorrectly.
Framing Error
Overflow Error
Overrun
Noise caused data corruption
during communications.
The connectors of the con-
necting cable are not con-
nected correctly.
Buffer Overflow The NT20 receive buffer is
(NT20-ST128 only) full.
<Error Description>
Parity Error
Overrun Error
Overflow Error
Framing Error
Buffer Overflow
Time Out
NAK Received
Unit No. Error
FCS Error
<Type of error>
Time Out
Cause
Check whether the parity bit,
frame length, baud rate, stop
bit length, and flow control
settings of the PLC match the
settings of the NT20.
Use a noise-resistant cable if
communications occurs in an
environment with high levels
of noise.
Reconnect the cable.
Lengthen the command trans-
mission intervals. If this error
occurs frequently, set flow
control for communications.
Section 7-2
Remedy
251