G.2
SEL-387-0, -5, -6 Relay Instruction Manual Date Code 20170601
Distributed Network Protocol
Configuration
The RTS signal can be used to control an external transceiver. The CTS signal
is used as a DCD input, indicating when the medium is in use. Transmissions
are only initiated if DCD is deasserted. When DCD drops, the next pending
outgoing message can be sent once an idle time is satisfied. This idle time is
randomly selected between the minimum and maximum allowed idle times
(i.e., MAXDLY and MINDLY). In addition, the SEL-387 monitors received
data and treats receipt of data as a DCD indication. This allows RTS to be
looped back to CTS in cases where the external transceiver does not support
DCD. When the SEL-387 transmits a DNP message, it delays transmitting
after asserting RTS by at least the time in the PREDLY setting. After
transmitting the last byte of the message, the SEL-387 delays for at least
PSTDLY milliseconds before deasserting RTS. If the PSTDLY time delay is
in progress (RTS still high) following a transmission and another transmission
is initiated, the SEL-387 transmits the message without completing the
PSTDLY delay and without any preceding PREDLY delay. The RTS/CTS
handshaking can be completely disabled by setting PREDLY to OFF. In this
case RTS is forced high and CTS is ignored, with only received characters
acting as a DCD indication. The timing is the same as above, but PREDLY
functions as if it were set to 0, and RTS is not actually deasserted after the
PSTDLY time delay expires.
PREDLY Settle time from RTS on to TX (OFF, 0.00–30.00 sec.) 0
PSTDLY Settle time after TX to RTS off (0.00–30.00 sec.) 0
ANADBA Analog reporting dead band (0–32767 counts) 100
ETIMEO Event data confirmation time-out (0.1–50.0 sec) 2.0
DRETRY Data link retries (0–15) 3
UNSOL Enable unsolicited reporting (Y, N) N
PUNSOL Enable unsolicited reporting at power-up (Y, N) N
REPADR DNP Address to report to (0–65534) 0
NUMEVE Number of events to transmit on (1–200) 10
AGEEVE Age of oldest event to transmit on (0–60 sec.) 2.0
Table G.1 Data Needed to Configure a Port for DNP (Sheet 2 of 2)
Label Description Default
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