I-4 MIRRORED BITS™ Date Code 20001006
SEL-351 Instruction Manual
The MIRRORED BITS protocol compatible with the Pulsar MBT-9600 modem is identical to the
standard MIRRORED BITS protocol with the following exceptions:
The relay injects a delay (idle time) between messages. The length of the delay is one relay
processing interval.
Note: An idle processing interval guarantees at least 19 idle bits at 9600 baud in an SEL-321
Relay with the system frequency at 65 Hz.
The relay resets RTS (to a negative voltage at the EIA-232 connector) for MIRRORED BITS
communications using this specification. The relay sets RTS (to a positive voltage at the EIA-232
connector) for MIRRORED BITS communications using the R6 or original R version of MIRRORED
BITS.
SETTINGS
protocol (SEL,LMD,MBA,MBB,MB8A,MB8B) PROTO = MBA ?
Set PROTO = MBA or MB8A to enable the MIRRORED BITS protocol channel A on this port. Set
PROTO = MBB or MB8B to enable the MIRRORED BITS protocol channel B on this port. The
standard MIRRORED BITS protocols MBA and MBB use a 7-data bit format for data encoding.
The MB8 protocols MB8A and MB8B use an 8-data bit format, which allows MIRRORED BITS to
operate on communication channels requiring an 8-data bit format. For the remainder of this
section, PROTO = MBA is assumed.
baud rate (300-38400) SPEED = 9600 ?
Use the SPEED setting to control the rate at which the MIRRORED BITS messages are transmitted,
in power system cycles (~), based on the following table:
SPEED SEL-321 SEL-351
38400 1 message per 1/8 cycle 1 message per 1/4 cycle
19200 1 message per 1/8 cycle 1 message per 1/4 cycle
9600 1 message per 1/4 cycle 1 message per 1/4 cycle
4800 1 message per 1/2 cycle 1 message per 1/2 cycle
enable hardware handshaking (Y,N,MBT) RTSCTS= N ?
Use the MBT option if you are using a Pulsar MBT 9600 baud modem. With this option set, the
relay will transmit a message every 1/2 power system cycle and the relay will deassert the RTS
signal on the EIA-232 connector. Also, the relay will monitor the CTS signal on the EIA-232
connector, which the modem will deassert if the channel has too many errors. The modem uses the
relay’s RTS signal to determine whether the new or old MIRRORED BITS protocol is in use.
Courtesy of NationalSwitchgear.com
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