Siemens LOGO! Series Manual page 194

LOGO! functions
4.4 Special functions list - SF
Backup of the real-time clock
The internal real-time clock of LOGO! is buffered against power failure. The buffering time is
influenced by the ambient temperature, and is typically 80 hours at an ambient temperature
of 25°C. 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.
Sample configuration
The output of a LOGO! is to be set annually on March 1, reset on April 4, set again on July 7,
and reset again on November 19. You need to configure two yearly timers with
corresponding on-times. Then logically link the outputs by means of an OR block.
Result
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Manual, 04/2011, A5E03556174-01
LOGO!