Schweitzer Engineering SEL-387-0, Instruction Manual

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F.2
SEL-387-0, -5, -6 Relay Instruction Manual Date Code 20170601
Unsolicited SER Protocol
Functions and Function Codes
will wait about 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.
Step 3. Upon receiving an acknowledge message with a matching
response number, the relay increments the response number
and continues to send and seek acknowledgment for unsolicited
SER messages, if additional SER records are available. When
the response number reaches three, it wraps around to zero on
the next increment.
Functions and Function Codes
In the messages shown below, all numbers are in hexadecimal unless
otherwise noted.
0x01 - Function Code:
Enable Unsolicited
Data Transfer
Upon power-up, the SEL-387 disables its own unsolicited transmissions. This
function enables the SEL-387 to begin sending unsolicited data to the device
which sent the enable message, if the SEL-387 has such data to transfer. The
message format for function code 0x01 is shown below.
The SEL-387 verifies the message by checking the header, length, function
code, and enabled function code against the expected values. It also checks the
entire message against the CRC-16 field. If any of the checks fail, except the
function code or the function to enable, the message is ignored.
If an acknowledge is requested as indicated by the least significant bit of the
status byte, the relay transmits an acknowledge message with the same
response number received in the enable message.
The “nn” field is used to set the maximum number of SER records per
message. The relay checks for SER records approximately every 500 ms. If
there are new records available, the relay immediately creates a new
unsolicited SER message and transmits it. If there are more than “nn” new
records available, or if the first and last records are separated by more than 16
seconds, the relay will break the transmission into multiple messages so that
no message contains more than “nn” records, and the first and last records of
each message are separated by no more than 16 seconds.
Data Description
A546 Message header
12 Message length in bytes (18 decimal)
0000000000 Five bytes reserved for future use as a routing address
YY Status byte (LSB = 1 indicates an acknowledge is requested)
01 Function code
C0 Sequence byte (Always C0.
Other values are reserved for future use in multiple frame messages.)
XX Response number (XX = 00, 01, 02, 03, 00, 01...)
18 Function to enable (0x18 - unsolicited SER messages)
0000 Reserved for future use as function code data
nn Maximum number of SOE records per message, 01 - 20 hex)
cccc Two byte CRC-16 check code for message