5.6
SEL-551 Relay Instruction Manual Date Code 20110408
Serial Port Communications and Commands
Communications Protocol
The CAN character (ASCII hex 18) aborts a pending
transmission. This is useful in terminating an unwanted
transmission.
Control characters can be sent from most keyboards with the following
keystrokes:
XON: <Ctrl+Q> (hold down the Control key and press Q)
XOFF: <Ctrl+S> (hold down the Control key and press S)
CAN: <Ctrl+X> (hold down the Control key and press X)
SEL Distributed Port Switch Protocol (LMD)
The SEL LMD Protocol permits multiple SEL relays to share a common
communications channel. The protocol is selected by setting the port setting
PROTOCOL = LMD. See Appendix C: SEL Distributed Port Switch Protocol
for more information on SEL LMD protocol.
SEL Fast Meter Protocol
SEL Fast Meter protocol supports binary messages to transfer metering and
control messages. The protocol is described in Appendix D: Configuration,
Fast Meter, and Fast Operate Commands.
SEL Compressed ASCII Protocol
SEL Compressed ASCII protocol provides compressed versions of some of
the relay ASCII commands. The protocol is described in Appendix E:
Compressed ASCII Commands.
Modbus RTU Protocol
Modbus RTU protocol provides binary multidrop communication with the
SEL-551. The protocol is described in Appendix G: Modbus RTU
Communications Protocol.
Serial Port Settings
Serial port settings for each protocol are listed in Table 5.2.
Table 5.2 Communications Settings (Sheet 1 of 2)
Field Description Screen Name Range Default
PROTOCOL = SEL
Port Protocol PROTOCOL SEL, LMD, MOD SEL
Baud Rate SPEED 300, 1200, 2400, 4800, 9600, 19200, 38400 2400
Number Data Bits DATA_BITS 7, 8 8
Parity PARITY O, E, N (O = Odd, E = Even, N = None) N
Stop Bits STOP 1, 2 1
Timeout TIMEOUT 0–30 minutes 15
Automatic Message Output AUTO Y or N N
Enable Hardware Handshaking RTS/CTS Y or N N
Fast Operate Enable FAST_OP Y or N N
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