6-12 Settings Date Code 20010518
SEL-2020 Instruction Manual
While you are transparently communicating through the SEL-2020, Fast Meter binary data will
continue to be collected and Fast Operate control operations will continue to be sent. If you
attempt a Fast Meter or Fast Operate request via the transparent connection, your request and
the automatic request may collide, leading to neither taking place. If you plan to use Fast Meter
or Fast Operate commands while transparently connected, you should disable any automatic
Fast Meter collection and Fast Operate control to avoid these collisions.
The SEL-2020 requires a three-step procedure to terminate transparent communications. This
three-step procedure helps ensure that transparent mode is not accidentally terminated by normal
data communications. The three-step process includes an initial channel idle time (set with
TERTIME1), a termination character sequence (set with TERSTRING), and a second channel
idle time (set with TERTIME2). All of these items are user-definable and can be set such that
they are not used when less security is required. The SEL-2020 default termination sequence has
the first time delay set to 1 second, the termination character set to <EOT> (end of transmission
character, ASCII character 4, <CTRL-D> on most keyboards), and the second time delay set to 0.
Direct Transparent Mode
The SEL-2030 normally uses data buffering when transferring data through transparently
connected ports. Some non-SEL IED protocols are intolerant of this data buffering since the
buffering introduces random inter-character time delays into the data stream. The SEL-2030
includes a Direct Transparent mode that eliminates these inter-character delays while
maintaining the buffering effectiveness. The Direct Transparent mode inter-character delay is
typically less than 1 millisecond and never exceeds 2 milliseconds. The Direct Transparent
mode is available on any rear-panel Master port, however is not available on the front Master
port.
To select the Direct Transparent mode, add the D parameter to the Port command (Port n D,
where n selects the port number). The SEL-2030 passes characters through rapidly, without
significant buffering delays. Therefore no handshaking is required if the Master and Slave port
baud rates match. Hardware handshaking may be required if the Master and Slave port baud
rates do not match. Software handshaking (XON/XOFF) is not supported by the SEL-2030 in
Direct Transparent mode, regardless of the XON_XOFF port setting. However, XON/XOFF
characters pass through the transparent port connection, allowing the connected devices to use
software handshaking independent of the SEL-2030.
The Direct Transparent mode (D parameter) typically should not be used when transparently
connecting to SEL devices. SEL interleaved binary messages (binary 20METER, 20TARGET,
etc.) are not supported during Direct Transparent mode connections.
Data Flow Control
All SEL devices, including the SEL-2020, support XON/XOFF software data flow control.
The
SEL-2020 also supports RTS/CTS hardware data flow control. If the device connected to an
SEL-2020 port has XON/XOFF software data flow control capability, you should enable this
flow control method on both the SEL-2020 and the connected device. You should use RTS/CTS
hardware data flow control only if the connected device has RTS/CTS capability and does not
have XON/XOFF capability. In either case, both the SEL-2020 and the connected device must
have the same data flow control method enabled.
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