Date Code 20010521
Unsolicited SER Protocol
F-1
SEL-387E Instruction Manual
APPENDIX F: UNSOLICITED SER PROTOCOL
I
NTRODUCTION
This appendix describes special binary Sequential Events Recorder (SER) messages that are not
included in
Section 9: Event Reports and Sequential Events Reporting
of the instruction
manual. Devices with embedded processing capability can use these messages to enable and
accept unsolicited binary SER messages from the SEL-387E Relay.
SEL relays and communications processors have two separate data streams that share the same
serial port. The normal serial interface consists of ASCII character commands and reports that
are intelligible to people using a terminal or terminal emulation package. The binary data
streams can interrupt the ASCII data stream to obtain information and then allow the ASCII data
stream to continue. This mechanism allows a single communications channel to be used for
ASCII communications (e.g., transmission of a long event report) interleaved with short bursts of
binary data to support fast acquisition of metering or SER data. To exploit this feature, the
device connected to the other end of the link requires software that uses the separate data
streams. The binary commands and ASCII commands can also be accessed by a device that does
not interleave the data streams.
Note: Make Sequential Events Recorder (SER) Settings With Care
The relay triggers a row in the Sequential Events Recorder (SER) event report for any change of
state in any one of the elements listed in the SER1, SER2, SER3, or SER4 trigger settings.
Nonvolatile memory is used to store the latest 512 rows of the SER event report so they can be
retained during power loss. The nonvolatile memory is rated for a finite number of “writes.”
Exceeding the limit can result in an EEPROM self-test failure. An average of four state changes
per minute can be made for a 25-year relay service life.
R
ECOMMENDED
M
ESSAGE
U
SAGE
Use the following sequence of commands to enable unsolicited binary SER messaging in the
SEL-387E Relay:
1. On initial connection send the
SNS
command to retrieve and store the ASCII names for the
digital I/O points assigned to trigger SER records. The order of the ASCII names matches
the point indices in the unsolicited binary SER messages. Send the "Enable Unsolicited Data
Transfer" message to enable the SEL-387E Relay to transmit unsolicited binary SER
messages.
2. When SER records are triggered in the SEL-387E, the relay responds with an unsolicited
binary SER message. If this message has a valid checksum, it must be acknowledged by
sending an acknowledge message with the same response number as contained in the
original message. The relay will wait approximately 100 ms to 500 ms to receive an
acknowledge message, at which time the relay will resend the same unsolicited SER
message with the same response number.
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