Date Code 20090730 Instruction Manual SEL-734 Meter
Appendix B
SEL Distributed Port
Switch Protocol (LMD)
Overview
SEL Distributed Port Switch Protocol (LMD) permits multiple SEL meters to
share a common communications channel. It is appropriate for low-cost,
low-speed port switching applications where updating a real-time database is
not a requirement.
Settings
Use the front-panel pushbuttons or the serial port SET P command to activate
the LMD protocol. Change the port PROTO setting from the default SEL to
LMD to reveal the following settings:
➤ PREFIX: One character to precede the address. This should be
a character that does not occur in the course of other
communications with the meter. Valid choices are one of the
following: @, #, $, %, &. The default is @.
➤ ADDR: Two-character ASCII address. The range is 01 to 99.
The default is 01.
➤ SETTLE: Time in seconds that transmission is delayed after
the request to send (RTS line) asserts. This delay
accommodates transmitters with a slow rise time.
Operation
1. The meter ignores all input from this port until it detects the
prefix character and the two-byte address.
2. Upon receipt of the prefix and address, the meter enables echo
and message transmission.
3. Wait until you receive a prompt before entering commands, to
avoid losing echoed characters while the external transmitter is
warming up.
NOTE: You can use the front-panel
pushbuttons to change the port
settings to return to SEL protocol.
4. Until the meter connection terminates, you can use the standard
commands that are available when PROTO is set to SEL.
Courtesy of NationalSwitchgear.com
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