F-2
Unsolicited SER Protocol
Date Code 20010521
SEL-387E Instruction Manual
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.
F
UNCTIONS AND
F
UNCTION
C
ODES
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-387E Relay disables its own unsolicited transmissions. This function
enables the SEL-387E Relay to begin sending unsolicited data to the device which sent the
enable message, if the SEL-387E has such data to transfer. The message format for function
code 0x01 is shown below.
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
The SEL-387E Relay 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.
If the function to enable is not 18 or the function code is not recognized, the relay responds with
an acknowledge message containing a response code 01 (function code unrecognized), and no
