10.7
Date Code 20080213 Instruction Manual SEL-351A Relay
Serial Port Communications and Commands
Communications Protocol
(ASCII 03). Each line of the message ends with a carriage
return and line feed.
3. The relay implements XON/XOFF flow control.
The relay transmits XON (ASCII hex 11) and asserts the RTS
output (if hardware handshaking enabled) when the relay input
buffer drops below 25 percent full.
The relay transmits XOFF (ASCII hex 13) when the buffer is
over 75 percent full. If hardware handshaking is enabled, the
relay deasserts the RTS output when the buffer is
approximately 95 percent full. Automatic transmission sources
should monitor for the XOFF character so they do not
overwrite the buffer. Transmission should terminate at the end
of the message in progress when XOFF is received and may
resume when the relay sends XON.
4. You can use the XON/XOFF protocol to control the relay
during data transmission. When the relay receives XOFF
during transmission, it pauses until it receives an XON
character. If there is no message in progress when the relay
receives XOFF, it blocks transmission of any message
presented to its buffer. Messages will be accepted after the
relay receives XON.
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 Distributed Port Switch Protocol (LMD) permits multiple SEL
relays to share a common communications channel. The protocol is selected
by setting the port setting PROTO = LMD. See Appendix C: SEL Distributed
Port Switch Protocol for more information.
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.
Courtesy of NationalSwitchgear.com
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