Mitsubishi Q2ACPU User Manual page 340

21. MAINTENANCE AND INSPECTION
(2) Memory card battery replacement procedure
Replace the memory card battery according to the following procedure when the life
is over. Even if the battery is removed, the memory card memory is backed up by a
capacitor so that the battery can be replaced while the memory card is out of the
CPU module.
However, if the time taken to replace the battery exceeds the guaranteed value
indicated in Table 21.6 below, the contents of the memory may be lost. Therefore,
change the battery as quickly as possible. While the PLC power is ON, the battery
can be replaced without removing the memory card in the CPU module. In this case,
the memory contents are backed up by the power supply voltage from the power
supply module.
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