TIMEKEEPER NVRAMs build on ST's ZEROPOWER
NVRAMs by adding non-volatile Real-Time Clocks. The Automatic
Battery Switchover and Write Protect circuits are extended to
the RTC section where counter-registers keep track of year, month,
day, date, hours, minutes, and seconds. A low-power 32KHz oscillator
provides the timing. It is optimized to draw only a tiny amount
of current - as low as 40nA - so it adds only a small additional
load to the battery. The RTC registers are mapped into the LPSRAM.
Eight to 16 bytes of the LPSRAM are replaced by the RTC registers.
The day, date, and time are read and written just like RAM locations. |
