J.5
Date Code 20170927 Instruction Manual SEL-751 Relay
MIRRORED BITS Communications
Settings
Use the CBADPU setting to determine the ratio of channel down time to the
total channel time before the meter element CBADA is asserted. The times
used in the calculation are those that are available in the COM records. See the
COMMUNICATIONS Command in Section 7: Communications for more
information.
MIRRORED BITS Protocol for the Pulsar 9600 Modem
To use a Pulsar MBT modem, set setting PROTO := MBTA or MBTB (Port
settings). Setting PROTO := MBTA or MBTB hides setting SPEED (forces
the data rate to 9600 bps), hides setting PARITY (forces parity to a value of 0),
hides setting RTSCTS (forces RTSCTS to a value of N), and forces the
transmit time to be faster than double the power system cycle. Tabl e J.4 shows
the difference in message transmission periods without use of the Pulsar
modem (PROTO MBTA or MBTB), and with use of the Pulsar MBT
modem (PROTO = MBTA or MBTB).
NOTE: You must consider the idle
time in calculations of data transfer
latency through a Pulsar MBT modem
system.
The relay sets RTS to a negative voltage at the EIA-232 connector to signify
that M
IRRORED BITS communications matches this specification.
Settings
Set PROTO = MBA or MB8A to enable the MIRRORED BITS protocol channel
A on this port. Set PROTO = MBB or MB8B to enable the M
IRRORED BITS
protocol channel B on this port. The standard M
IRRORED BITS protocols MBA
and MBB use a 6-data bit format for data encoding. The MB8 protocols
MB8A and MB8B use an 8-data bit format, which allows M
IRRORED BITS to
operate on communications channels requiring an 8-data bit format. For the
remainder of this section, PROTO = MBA is assumed. Table J.5 shows the
M
IRRORED BITS protocol port settings, ranges, and default settings for Port F,
Port 2, Port 3, and Port 4.
Ta b le J . 4 MIRRORED BITS Communications Message Transmission Period
Data Rate PROTO MBTA or MBTB PROTO = MBTA or MBTB
38400 4 times a power system cycle n/a
19200 4 times a power system cycle n/a
9600 4 times a power system cycle 2 times a power system cycle
4800 7.5 ms n/a
Ta b le J . 5 M IRRORED BITS Protocol Settings (Sheet 1 of 2)
Setting
Prompt
Setting Description
Fac to ry
Default
Setting
TXID MIRRORED BITS ID of This Device (1–4) 2
RXID M
IRRORED BITS ID of Device Receiving From (1–4) 1
RBADPU Outage Duration to Set RBAD (0–10000 seconds) 60
CBADPU Channel Unavailability to Set CBAD (1–10000 ppm) 1000
RXDFLT 8 char string of 1s, 0s, or Xs XXXXXXXX
RMB1PU RMB1 Pickup Debounce Messages (1–8 messages) 1
RMB1DO RMB1 Dropout Debounce Messages (1–8 messages) 1
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