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 BITS communications data on the same serial port. See SEL MIR-
RORED BITS Communication on page 15.31 for more information on MIRRORED
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 BITS communications. If you have
enabled both of the M
IRRORED BITS 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 MIR-
RORED BITS 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 BITS), 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.
Ta b l e 1 4.80 L O O P C o m m a n d
Command Description Access Level
LOOP Begin loopback of a single enabled MIRRORED BITS 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 MIRRORED BITS 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 BITS 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 BITS 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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