K.3
Date Code 20060320 Instruction Manual SEL-311C Relay
Unsolicited Fast SER Protocol
Recommended Message Usage
Recommended Message Usage
Use the following sequence of commands to enable unsolicited Fast SER
messaging in the SEL-311C:
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 Fast SER messages. Send the “Enable Unsolicited
Data Transfer” message to enable the SEL-311C to transmit
unsolicited Fast SER messages.
2. When SER records are triggered in the SEL-311C, the relay
responds with an unsolicited Fast 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 Fast SER message with the same response number.
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 Fast SER
messages, if additional SER records are available. When the
response number reaches three, it wraps around to zero on the
next increment.
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