The power supply of SRAM is selected from the highest voltage of I-7188 (VCC). The initial voltage of battery is about 3V. If the I-7188 is power on, the I-7188 series (VCC) will be about 5V. If the I-7188 is off, the I-7188 (VCC) will be about 0V. So when the I-7188's power is on, the I-7188 (VCC) will supply power to SRAM. In this condition, the battery will be preserved for later usage.
If I-7188's power is off, the battery with higher voltage will supply power to SRAM. The stored data of SRAM will remain if the power is larger then 2.0V.
When I-7188's power is off, the power control circuit will select the battery with higher voltage to backup SRAM. X608's batteries can be replaced, but the data stored in SRAM will be lost.
The X608 can provide between three and five years (Shutdown 24 hours everyday) of backup time over a nine years period.
