Battery; Protections Against Power Failure - Omron SYSMAC C Series User Manual

Installing the C20
When the I/O expansion unit is used with the CPU, the FG terminals on
both devices are used for grounding.
Battery
The CPU has a built-in battery to back up the memory in case of power
failure. This backup battery is required regardless of whether a RAM or
EPROM chip is used as the program memory. The battery's service life is
about five years when the PC is used at a temperature of 25°C, and is
somewhat shortened in temperatures higher than this or where humidity
is unusually high. These factors should also be kept in mind when storing
the PC.
When the battery is almost completely discharged, the ALARM/ERROR
indicator on the CPU blinks. You then have one week to change the
battery before memory loss occurs. A fresh battery must be installed
within 3 minutes after the old one has been removed from its connector.
Protections against power failure
A power sequence circuit is incorporated in the PC to prevent
malfunctioning because of a momentary power failure or a drop in the
supply voltage.
If the voltage drops below 85%, the PC stops operating and the external
output relays are automatically turned off.
ACH
PF
(power failure " | detection time | =
detection signal) : $5 jo
+5Ve
GRE {power reset]
co
4$
Approx. c
10msec Approx. 1sec k
$f
Relay output
2-7