User`s manual

Maintenance and inspection Resuming operation of CPU after storage
10 – 22
10.4 Resuming operation of CPU after storage
The content of the memory is kept by the battery, even if the CPU or memory card is stored or
if the power supply of the PLC hasn’t been switched on over a long time. Refer to section 10.3.1
for the life time of the batteries. (The power-on time ratio is 0 %, when the power supply is
switched off or during storage.)
Data may be lost,
– if the CPU or memory card is stored witout battery.
– if a battery is installed, but the battery voltage falls under the minimum value during storage.
Buffer battery of the CPU
If the CPU battery is missing or discharged, format the following memory areas by the program-
ming software GX Developer or GX IEC Developer, before operating the CPU:
– Program memory
– Standard RAM.
To format a program memory during boot operation, select the "Clear program memory" check-
box in the Boot file tab of the PLC parameter dialog box.
Buffer battery of the SRAM memory card
If the SRAM memory card battery is missing or discharged, format the memory card, before
operating the CPU too.
NOTES
Data in the CPU standard ROM and in Flash and ATA memory cards don’t need battery buff-
ering. The data will not be lost even after demounting or at battery failure.
When using the function of storing latch data into the standard ROM with the universal
model CPU PLC, these data will not be lost even after demounting or at battery failure.
Save all data from the CPU and from the memory card by the programming software GX
Developer or GX IEC Developer, before storage or shutting off the power supply of the PLC.
When the programmable controller is powered on or the CPU module is reset, the CPU
module initializes all of the following data if an error is detected:
– Program memory data
– Standard RAM data
– Error history
– Latch data (latch relay (L), devices in latch setting range set in the parameter, special
relay SM900 to SM999, special register SD900 to SD900)
– Sampling trace data