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9-2SectionBoard Replacement
129
9-2-3 1:N NT Link Mode
Serial commu-
nications
mode
Indicator
display
Status
information,
etc.
I/O memory Cause Remedy
Serial commu-
nications mode
is not set to NT
Link.
--- --- Bits 12 to 15
(Serial Commu-
nications Mode)
of DM 6555/
DM 6550 are
set to a value
other than
5 Hex.
Serial communica-
tions mode is not
set correctly.
Set bits 12 to 15 (Serial
Communications Mode) of
DM 6555/ DM 6550 to
5 Hex.
Serial commu-
nications mode
is set to NT
Link.
The COMMj
indicators do
not flash at all.
(Communica-
tions have not
been electrical-
ly established.)
--- --- There is a hardware
error.
Conduct a loopback test in
serial communications
mode to check the trans-
mission lines. If an error
occurs during the test, re-
place the Serial Commu-
nications Board.
The SD and
COMMj indi-
cators are
--- ---
There is a setting
error for the PT seri-
al port.
Correct the PT serial port
settings.
flashing, but the
Serial Commu-
nications Board
cannot commu-
nicate with the
Programmable
Terminal (PT).
The I:N NT Link unit
number of the PT is
incorrect.
The same 1:N NT
Link unit number
has been set for
more than one PT
Review the NT Link unit
number of the PT.
The maximum al-
lowable NT Link unit
number is incorrect-
ly set for the sys-
tem.
Review the PC Setup set-
tings.
Cables are incor-
rectly connected.
The RS-422A/485
port setting (2-wire
or 4-wire) is incor-
rect.
Adapters such as
the NT-AL001-E are
incorrectly wired or
set.
Review the wiring or
switch settings.
A communications
error frequently oc-
curs due to noise,
etc.
Review the wiring and
installation environment.
There is a PT hard-
ware error.
Replace the PT.