J.4
SEL-351A Relay Instruction Manual Date Code 20080213
SEL-351A Fast SER Protocol
Functions and Function Codes
Functions and Function Codes
In the messages shown below, all numbers are in hexadecimal unless
otherwise noted.
01-Function Code:
Enable Unsolicited
Fast SER Data
Transfer, Sent From
Master to Relay
Upon power up, the SEL-351A disables its own unsolicited transmissions.
This function enables the SEL-351A to begin sending unsolicited data to the
device which sent the enable message, if the SEL-351A has such data to
transfer. The message format for function code 01 is shown in Table J.1.
The SEL-351A 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 Fast SER message and transmits it. If there are more than “nn”
new records available, or if the first and last record 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 record
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 functions are enabled. If the SER
triggers are disabled (SER1, SER2, and SER3 are all set to NA), the
unsolicited Fast SER messages are still enabled, but the only SER records
generated are due to settings changes, and power being applied to the relay. If
the SER1, SER2, or SER3 settings are subsequently changed to any non-NA
value and SER entries are triggered, unsolicited SER messages will be
generated with the new SER records.
Table J.1 Message Format for Function Code 01
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 (18—unsolicited SER messages)
0000 Reserved for future use as function code data
nn Maximum number of SER records per message, 01–20 hex
cccc Two byte CRC-16 check code for message
Courtesy of NationalSwitchgear.com
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