User memory is preserved only if the compatible Energy Pack is connected (and charged)
at power-down.
If the Energy Pack is connected at power-up, the CPU waits for it to charge up before
beginning normal operations. For CPE330/CPE400/CPL410, this typically takes up to 90
seconds.
In the event the Energy Pack fails to charge up in a reasonable amount of time, or is
absent, the CPU will time out the wait period and will then commence operations without
the Energy Pack. When this occurs, the CPU is vulnerable to loss of memory, should
another power failure occur. It is critical to monitor the status bits shown in Energy Pack
Status Bit Operation so that human intervention can be summoned.
Removing or reconnecting the Energy Pack while the connected CPU is powered off has
no effect on the preservation of user memory.
Note: Because the Time of Day (TOD) clock is powered by a separate Real Time Clock
battery in CPE302/CPE305/CPE310/CPE330/CPE400/CPL410, the Energy Pack has no
effect on the CPU TOD value.
4.10.3.3.1 Energy Pack Status Bit Operation
As shown in the table below, the CPU application program can monitor the status of the
attached Energy Pack via %S0014 (PLC_BAT) and %SA0011 (LOW_BAT). For more details,
refer to the Section on Diagnostics in PACSystems and RX3i CPU Programmer’s Reference
Manual, GFK-2950.
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