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CTI Janus Programmable Automation Controller IOG
8.3.4
Clock Settings
Determines how the controller clock is set
•
Set Current Time
–
Enables manual entry of the date and time.
o
Date (in YYYY-MM-DD format)
o
Local Time (formatted as HH:MM AM/PM)
•
Remote NTP Server
–
Obtains date and time from an NTP (Network Time Protocol) server.
The NTP Server poll rate is determined by the clock discipline algorithm designed to maximize accuracy
while minimizing network overhead. The actual poll interval depends on clock accuracy and offset
differences, called
“clock jitter”. The algorithm also includes provisions to further reduce network load
when the NTP Server is unreachable.
The NTP specifications allow one large time adjustment when first connected to the server, but avoids
additional large corrections. This means it may take a few hours to correct a clock that was set incorrectly
after the system was started.
The Janus controller monitors the connection to the Remote NTP Server and generates Error 595 (Remote
NTP Server Error) and logs an event when the connection is lost. The status of the connection is checked at
startup (or when ‘Sync Time Method’ on the
Clock Settings
webpage is changed to ‘Use Remote NTP Server’)
and periodically every hour. The error condition is cleared and event logged when communications is
received from the NTP Server.
The following must be entered wh
en ‘Remote NTP Server’ selected:
•
Time Zone Region
•
Time Zone City
•
Sync Host IP Address
•
CTI Data Cache Host PLC
The CTI Data Cache interface reads time from the Host PLC immediately after the connection/validation
process and in following cases:
o
The Host PLC indicates the PLC Clock time/date has been changed,
o
Approximately every 2 hours.
When the [A
PPLY
] button is pressed, entries will be validated and error message displayed if necessary. If
no errors are detected, a confirmation message will be displayed. The new parameters go into effect
immediately after the message is acknowledged,.
