User Manual

Siemens Building Technologies VISONIK DCS Functions and System Messages VVS18 CM2U8567E / 04.1999
Landis & Staefa Division Function DATE 2-69
2.9 DATE Set Date and Time
For various Functions (e.g. TRR, DRR, MXD, etc.) to work correctly, VISONIK requires
to know the actual time, date and day.
If the system time is undefined then anywhere throughout the whole VISONIK system
where time is displayed (outputs), two question marks are given in place of hours (e.g.:
??:34:27). But the printed minutes and hours do not agree with the correct time.
Function DATE is used to manually set up the date, time and day through a VISONIK
system. It therefore defines the new Server time which is also automatically transferred
to all process stations.
Date and time are automatically transferred after being set. Different numbers of days in
months, leap years, summer/winter time changeover and special day programming are
taken into account. Date and time are synchronised from the VISONIK Server.
In principle, all time-dependent (PS, partner systems in a LINK System, ECUs) receive
the time (so-called 'System time') from the Server, as follows:
–
Every minute the Server transmits via SDLC Rings a
synchronising impulse
to all its
partners. Each partner compares this impulse with its own clocked minute. If a certain
tolerance is exceeded the respective partner's clock is corrected.
–
Every 8 minutes the Server transmits a
time message
with date, day and time to all
partners. Such a time message may also include summer/winter time data.
Note: One exception to time synchronisation is the case where an optional MASTER
clock process station is involved.
MOTHER Clock Function
System time may also be synchronised to an external (Mother) clock, in which case only
minute impulses can be accepted by the system and not the absolute time.
2.9.1 Influence of MCPS and BKPS on System Time
The BKPS parameter allows determining whether the time upon the start of the DCS
should be taken from a process station or not.
The value of the MCPS parameter identifies the process station from which the time in
the DC Server is specified or monitored.
When MCPS=0 and BKPS=No then the following holds in general for the determination
of system time and date:
–
On start-up the Server takes the last saved time from its hard disk as the system time.
This time is not clocked during the time of certain operational interruptions (e.g. power
failure). All system partners are then set to this system time.
Note: The actual time must be set correctly by the operator using Function DATE.
Manual setting of time can be made through any terminal, i.e. also through a partner
system's terminal. The corrected actual time will then be transmitted to all partners via
the Master system.
BACKUP Function
A VISONIK DCS has no clock battery buffer which means the clock stops during certain
interruptions (e.g. system BOOT, power failure). However, process station (Controller)
clocks are battery buffered and continue to run.
–
If, now, the BACKUP Function (VISONIK parameter BKPS>0) is actioned and after an
interruption, the Server takes the first valid time from
any
suitable process station, or
in a LINK System
any
suitable system partner. The Server re-transmits this time to all
partners.
Time Synchronisation
BKPS=Yes/No0
MCPS=n