7.14
SEL-700G Relay
Instruction Manual
Date Code 20170814
Communications
SEL ASCII Protocol and Commands
SNTPRATE. If the NTP server does not respond with the period defined by
setting SNTPTO, then the relay tries the other SNTP server. When the relay
successfully synchronizes to the primary NTP time server, Relay Word bit
TSNTPP asserts. When the relay successfully synchronizes to the backup
NTP time server, Relay Word bit TSNTPB asserts.
ESNTP = MANYCAST
In the manycast mode of operation, the relay initially sends an NTP request to
the broadcast address contained in setting SNTPPSIP. The relay continues to
broadcast requests at a rate defined by setting SNTPRATE. When a server
replies, the relay considers that server to be the primary NTP server, and
switches to UNICAST mode, asserts Relay Word bit TSNTPP, and thereafter
requests updates from the primary server. If the NTP server stops responding
for time SNTPTO, the relay deasserts TSNTPP and begins to broadcast
requests again until the original or another server responds.
ESNTP = BROADCAST
If setting SNTPPSIP = 0.0.0.0 while setting ESNTP = BROADCAST,
the relay will listen for and synchronize to any broadcasting NTP server.
If setting SNTPPSIP is set to a specific IP address while setting ESNTP =
BROADCAST, then the relay will listen for and synchronize to only NTP
server broadcasts from that address. When synchronized, the relay asserts
Relay Word bit TSNTPP. Relay Word bit TNSTPP deasserts if the relay does
not receive a valid broadcast within five seconds after the period defined by
setting SNTPRATE.
SNTP Accuracy Considerations
SNTP time-synchronization accuracy is limited by the accuracy of the SNTP
Server and by the networking environment. The highest degree of SNTP time
synchronization can be achieved by minimizing the number of switches and
routers between the SNTP Server and the SEL-700G. Network monitoring
software can also be used to ensure that average and worst-case network
bandwidth use is moderate.
When installed on a network configured with one Ethernet switch between the
SEL-700G and the SNTP Server, and when using ESNTP = UNICAST or
MANYCAST, the relay time-synchronization error with the SNTP server is
typically less than ±1 millisecond.
SEL-700G and the SNTP Server, and when using ESNTP = UNICAST or
MANYCAST, the relay time-synchronization error with the SNTP server is
typically less than ±1 millisecond.
SEL ASCII Protocol and Commands
Message Format
SEL ASCII protocol is designed for manual and automatic communication.
All commands the relay receives must be of the following form:
<command><CR> or <command><CRLF>
NOTE:
The
<Enter>
key on most
keyboards is configured to send the
ASCII character 13 (
<Ctrl+M>
) for a
carriage return. This manual instructs
you to press the
<Enter>
key after
commands to send the proper ASCII
code to the SEL-700G.
Summary of Contents for SEL-700G Series
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