Backup Of The Real-Time Clock - Siemens LOGO! Series Manual

LOGO! functions
4.3 Special Functions
Accuracy of T
Because of slight tolerances in the characteristics of electronic components, the set time T
can deviate. You can find a detailed description of such deviations in the "On-delay" topic
(Page 160).
Accuracy of the timer (weekly/yearly timer)
To prevent timing inaccuracy of the real-time clock in C versions caused by this deviation,
the timer value is continuously compared with a high-precision timebase and corrected. The
resultant maximum timing inaccuracy is ±2 s/day.
4.3.3

Backup of the real-time clock

Because the internal real–time clock of a LOGO! is backed up, it continues operation after a
power failure. The ambient temperature influences the backup time. At an ambient
temperature of 25°C, the typical backup time of a LOGO! 0BA6 is 80 hours and the typical
backup time of a LOGO! 0BA7 is 20 days.
If there is a power outage of a LOGO! for more than 80 hours (if 0BA6) or 20 days (if 0BA7),
the internal clock responds, dependent on the equipment series, as shown below:
● Equipment series 0BA0:
● Equipment series 0BA1 to 0BA6:
● Equipment series 0BA6:
● Equipment series 0BA7
152
On restarting, the clock is set to "Sunday 00:00 1 January". The time starts to run. Due to
this, the system processes the time switches, which trigger actions if necessary.
On restarting, the clock is set to "Sunday 00:00 1 January". The time is stopped and
flashes. LOGO! is back in the status that it was in before the power outage. In RUN
mode, the system processes the counters that were parameterized with the time above.
The clock is, however, still stopped.
If you are using the optional LOGO! Battery card, or combined LOGO! Memory/Battery
card, LOGO! can retain the clock time for up to two years. These cards are available for
equipment series 0BA6.
On restarting, the clock is set to "Sa 00 00 2011-01-01". The time is stopped and flashes.
LOGO! is back in the status that it was in before the power outage. In RUN mode, the
system processes the counters that were parameterized with the time above. The clock
is, however, still stopped.
Manual, 04/2011, A5E03556174-01
LOGO!