6.8
SEL-587Z Instruction Manual
Date Code 20020903
Serial Port Communications
Communications Protocols
NOTE:
The <
Enter
> key on most
keyboards is configured to send the
ASCII character 13 (^M) for a carriage
return. This manual instructs you to
press the <
Enter
> key after commands,
which sends the proper ASCII code to
the relay.
The relay transmits all messages in the following format:
<STX><MESSAGE LINE 1><CRLF>
<MESSAGE LINE 2><CRLF>
•
•
•
<LAST MESSAGE LINE><CRLF><ETX>
Each message begins with the start-of-transmission character (ASCII 02) and
ends with the end-of-transmission character (ASCII 03). Each line of the
message ends with a carriage return and line feed.
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.
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:
SEL Distributed Port Switch Protocol (LMD)
SEL LMD Protocol permits multiple SEL relays to share a common
communications channel. The protocol is selected by setting the port setting
PROTO = LMD. See
SEL Distributed Port Switch Protocol (LMD) on
for more information on the 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
Control Characters
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)
Summary of Contents for SEL-587Z
Page 10: ...This page intentionally left blank ...
Page 12: ...This page intentionally left blank ...
Page 66: ...This page intentionally left blank ...
Page 106: ...This page intentionally left blank ...
Page 126: ...This page intentionally left blank ...
Page 162: ...This page intentionally left blank ...
Page 228: ...This page intentionally left blank ...