Backup Of The Real-Time Clock; Retentivity - Siemens LOGO! Manual

LOGO! functions
4.3 Special Functions
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 is 80 hours.
If there is a power outage of a LOGO! for more than 80 hours, the internal clock responds,
dependent on the equipment series, as shown below:
● Equipment series 0BA0:
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.
● Equipment series 0BA1 and later:
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 the RUN
status, the system processes the counters that were parameterized with the time above.
The clock is, however, still stopped.
● Equipment series 0BA6:
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.
4.3.4

Retentivity

The switching states, counter and time values of many SFs (see the "Special functions list -
SF (Page 119)" topic) can be set retentive. This means that current data values are retained
after a power failure, and that the block resumes operation at the break point. The timer is
not reset, but resumes operation until the time-to-go has expired, for example.
To enable this response, however, the relevant functions must be set retentive. Two options
are available:
R: The data is retained.
/: Current data is not retained (default). See the section in topic "Second circuit program
(Page 83)" on enabling and disabling retentivity.
The hours counter, weekly timer, yearly timer and PI controller are always retentive.
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Manual, 10/2017, A5E01248535-AA
LOGO!