14.35
Date Code 20171006
Instruction Manual
SEL-400 Series Relays
ASCII Command Reference
Command Description
LOOPBACK
Use the
LOOPBACK
command to instruct the relay to receive the transmitted
M
IRRORED
B
ITS
communications data on the same serial port. See
for more information on M
IRRORED
B
ITS
communications.
LOOP
The
LOOP
command puts the relay serial port in loopback if you have previ-
ously configured the port for M
IRRORED
B
ITS
communications. If you have
enabled both of the M
IRRORED
B
ITS
communications channels (A and B), then
you must specify the channel parameter. If you have only one of the channels
enabled, then the relay assumes that channel if you do not specify that channel in
the command. If you do not specify a time-out period, the relay provides a 5-min-
ute time-out.
You can enter the options in any order. If you operate the relay using both M
IR
-
RORED
B
ITS
communications channels (A and B), then you must specify the
channel parameter by using the
LOOP A
command and the
LOOP B
command.
When you issue the
LOOP
command, the relay responds with statements about
the loopback time, status of the RMB (Receive M
IRRORED
B
ITS
), and
Are you
sure (Y/N)?
. If you answer
Y <Enter>
, the relay responds with
Loopback Mode
Started
.
In the loopback mode, ROK drops out and the relay uses LBOK to indicate
whether the data transmissions are satisfactory. The relay collects COM data as
usual. Time synchronization and virtual terminal modes are not available during
loopback. The relay continues passing analog quantities.
Table 14.80
LOOP Command
Command
Description
Access Level
LOOP
Begin loopback of a single enabled M
IRRORED
B
ITS
commu-
nications channel (either Channel A or Channel B) for 5 minutes;
ignore input data and force receive bits (RMB) to defaults.
P, A, O, 2
LOOP
c
a
a
Parameter
c
is A or B, representing Channel A or Channel B.
Begin loopback of M
IRRORED
B
ITS
communications
Channel
c
for 5 minutes; ignore input data and force receive
bits (RMB) to defaults.
P, A, O, 2
LOOP
t
Begin loopback of a single M
IRRORED
B
ITS
communications
channel (either Channel A or Channel B) and end the loop-
back after time-out
t
minutes; ignore input data and force
receive bits (RMB) to defaults;
t
range is 1–5000 minutes.
P, A, O, 2
LOOP
t c
Begin loopback of a single M
IRRORED
B
ITS
communications
channel (either Channel A or Channel B) and end the loop-
back after time-out t minutes; ignore input data and force
receive bits (RMB) to defaults;
t
range is 1–5000 minutes.
P, A, O, 2
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