Upon system startup, by default NetClock will not declare synchronization until one of the external references becomes available and valid.
This functionality can be overridden by enabling the Synchronize to Battery Backed Time on Startup, thus allowing the battery backed time to be used as System Time upon system startup. The Battery Backed Time is also referred to as the time maintained by the integrated Real Time Clock (RTC)
This will result in NetClock providing a System Time before one of the external references becomes available and valid. This will happen automatically, i.e. without user intervention. As soon an external reference will become available, its time will take precedence over the battery backed time: The System Clock will adjust the System Time for any time difference.
Note: The Battery Backed Time is also referred to as the time maintained by the integrated Real-Time Clock (RTC).
Using the Battery Backed Time on Startup is typically used in these cases:
- If the synchronization state is to be reached as quickly as possible, even if this means the time distributed initially will most likely be less accurate than an external time reference.
- A system is intended to operate autonomously (i.e. without any external references) and
- the hand-set time entered manually during commissioning of the system is sufficiently accurate
- the system needs to be able to completely recover from a temporary power loss, or similar, without human intervention.
- A system is used for simulation or testing purposes, and UTC traceability is not required.
… depends on the accuracy of the hand-set time if the time is set manually in an autonomous system. In a non-autonomous system (i.e, when using external reference(s)) NetClock's System Clock will regularly update the battery-backed time.
Another factor impacting the accuracy of the battery-backed time is how long a NetClock unit is powered off: Any significant amount of time will cause the battery-backed RTC to drift, i.e. the battery-backed time will become increasingly inaccurate.
When distributing a hand-set, battery backed time via NTP, please set the time relatively close to UTC, so as to prevent NTP synchronization problems when transitioning from the hand-set time to a UTC-based external input reference. See also Input Reference Priorities.
To use the battery-backed time as the synchronized time at start-up: