Sel SEL-421 - SEL Compressed ASCII Commands; Selected ASCII Control Characters

R.5.4
SEL-421 Relay Reference Manual Date Code 20111215
SEL Communications Protocols
Protocol Active When Setting PROTO := SEL
The <Enter> key on standard keyboards sends the ASCII character CR for a
carriage return. This manual instructs you to press the <Enter> key after
commands to send the proper ASCII code to the relay. A correctly formatted
command transmitted to the relay consists of the command, including optional
parameters, followed by either a CR character (carriage return) or CR and LF
characters (carriage return and line feed). The following line contains this
information in the format this manual uses to describe user input:
<command> <Enter> or <command> <Enter> <CR>
You may truncate commands to the first three characters. For example,
EVENT 1 <Enter> is equivalent to EVE 1 <Enter>. You may use upper- and
lowercase characters without distinction, except in passwords.
In response to a command, the relay may respond with an additional dialog
line or message. The relay transmits dialog lines in the following format:
<DIALOG LINE ><CR><LF>
The relay transmits messages in the following format:
<STX><MESSAGE LINE 1><CR><LF>
<MESSAGE LINE 2><CR><LF>
…
<LAST MESSAGE LINE><CR><LF>< ETX>
Each message begins with the start-of-transmission character, STX, and ends
with the end-of-transmission character, ETX. Each line of the message ends
with a carriage return, CR, and line feed, LF.
Send the CAN character to the relay to abort a transmission in progress. For
example, if you request a long report and want to terminate transmission of
this report, depress the <Ctrl> and <X> keys (<Ctrl+X>) to terminate the
report.
SEL Compressed ASCII Commands
The relay supports a subset of SEL ASCII commands identified as
Compressed ASCII commands. Each of these commands results in a comma-
delimited message that includes a checksum field. Most spreadsheet and
database programs can directly import comma-delimited files. Devices with
embedded processors connected to the relay can execute software to parse and
interpret comma-delimited messages without expending the customization
and maintenance labor needed to interpret nondelimited messages. The relay
calculates a checksum for each line by numerically summing all of the bytes
that precede the checksum field in the message. The program that uses the
data can detect transmission errors in the message by summing the characters
of the received message and comparing this sum to the received checksum.
Tabl e 5 . 3 S ele cte d ASC II Control Characters
Decimal Code Name Usage Keystroke(s)
13 CR Carriage return <Enter> or <RETURN>
or <Ctrl+M>
10 LF Line feed <Ctrl+J>
02 STX Start of transmission <Ctrl+B>
03 ETX End of transmission <Ctrl+C>
24 CAN Cancel <Ctrl+X>
17 XON Flow control on <Ctrl+Q>
19 XOFF Flow control off <Ctrl+S>