Chapter 4. CPU Operation
176 PACSystems* RX7i, RX3i and RSTi-EP CPU Reference Manual GFK-2222AD
4.11.3 Power Cycle Operation with an Energy Pack
Energy Packs offer distinct advantages over batteries:
a) significantly longer life cycles
b) they are more reliable
c) flammability during shipment is not an issue
d) in their end-of-life phase, their decline is a lot more gradual.
The system design includes the ability of the CPU and the Energy Pack to monitor each other in real time.
This permits the user to monitor alarms and thereby determine when to replace a capacitor pack. The
capacitor pack is normally replaced while the CPU is powered on, giving it time to charge up before any
subsequent loss of power. Users should target periods which are expected to be free from electrical
events, such as thunderstorms, to carry out such work. Capacitor packs may also be replaced while
power is off.
When power is lost, the Energy Pack supplies current and maintains voltage levels for a period of time
sufficient to permit the connected CPU to save all dynamic memory to non-volatile memory.
When power is restored, the CPU will not start running its application until the Energy Pack signals that
it is fully charged. The CPU will then resume operation using the contents of memory retained at the
previous loss of power event. The Energy Pack charges continuously during normal operation.
The RX3i and RX7i product lines encompass several different Energy Packs, so it is important to use
compatible products:
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, 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, the Energy Pack has no effect on the CPU TOD value.
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