7-3SectionMaintenance of the NT21
183
Error Details RemedyDisplayed Probable Cause
Time-out Error The connecting cables are not
connected correctly. (Send/Receive)
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 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 communication service of the
host is stopped. (Send/Receive)
Check that the host is capable of communicating
with the NT21 (confirm that the communication
settings of the host and NT21 match, and
connection between the host and NT21 if flow
control is set).
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. (6-9-10 Setting the Time-out Interval,
page
142) It may also be possible to solve the
problem by shortening the host cycle time.
PC Unit No. Error The unit # does not match that set
on the PC.
Re-set the unit number at the host side to 0.
Noise caused data corruption during
communication.
Carry out grounding work in accordance with the
conditions by referring to 3-1-4 Grounding
, page
18.
NAK received —— 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.
Undefined Command
The host is not supported. Check the PC model used for the host.
Error
Command level 3 is not effective. Check that the command level setting for the host is
level 1, 2, 3.
Data Over Flow Error Communication command from the
host is too long. (With memory link)
Set flow control method in the host.
Increase transmission interval.
Command transmission to the host
is not possible.
Check the communication cable.
Check the control method at the PT and the host.
Increase the baud rate if it is too slow.
7-3 Maintenance of the NT21
Carry
out maintenance work in order to ensure that the NT21 is always used in
its optimum condition.
WARNING
Do
not attempt to take
the Unit apart and do not touch any inter
-
nal parts while the power is being supplied. Doing either of
these may result in electrical shock.
Always back up the screen data and store it in a safe place in case a problem
develops and the NT21 needs to be replaced or repaired.
It
is advisable to have a spare NT21 available
to minimize system downtime in
the
event of an NT21 failure or if the screen display becomes dif
ficult to read due
to deterioration of the display unit.
Backing Up Screen Data
Preparing a Spare PT
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