Clock Functions And Synchronization; Rtu Clock; Time Adjustment And Synchronization - Motorola V186 - Cell Phone - GSM System Planner Manual

Clock Functions and Synchronization

RTU Clock

The ACE3600 RTU has one time source, an internal system clock which is in
microsecond resolution. This time source is updated using a backup source of the RTC
hardware component - Real Time Clock (seconds accuracy).
In addition, external clocks, such as GPS and NTP servers can be used as a time source.
See NTP Clock Synchronization and Global Positioning System (GPS) below.
The time resolution of the system clock is hour, minute, second, millisecond,
microsecond. The date resolution is day, month, year. Leap year support is automatic.
When the RTU first starts up, the system clock is set according to the RTC, which always
retains its time in seconds (even when the RTU is powered down.) The RTU time can
then be set using a number of mechanisms.
The RTU clock controls the date and time of the ACE3600 unit. Date and time
information is used for timestamps on events such as time tagging changes to time tagged
discrete inputs, etc.
The ACE3600 includes configurable time zone support, where RTUs in one time zone
can adjust messages received from another time zone. The time zone is commonly used
in conjunction with NTP servers and GPS receiver. These servers operate in UTC
(Universal Time Clock) which is in the (Greenwich Mean Time) GMT time zone. Setting
time zone in a unit will adjust it to the local time.
The ACE3600 also supports daylight savings time. Daylight savings time is used only in
conjunction with a time zone. The start and end dates for daylight savings time (month,
day, our) can be defined in the Daylight Saving Dates table. (The current year is
assumed.) The RTU will check these dates and adjust the time by one hour when
appropriate. The time zone is set in the STS site configuration and the daylight savings
time is set in the application system table.

Time Adjustment and Synchronization

MDLC time synchronization of the RTU clock can be performed locally or remotely,
using MDLC protocol over a variety of communication media, including conventional
radio, RS485, and RS232. Synchronization is accurate to 1 millisecond+0.5 (very low
delay). With IP media, this feature can be enabled, but because its accuracy/delay is
unpredictable it is not recommended. NTP, the recommended method of obtaining the
time over IP media (PPP or Ethernet), allows accuracy of 1 to 100 milliseconds
depending on the media.
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