DS1689_05 Datasheet, PDF (23/36 Pages) Dallas Semiconductor – 3V/5V Serialized Real-Time Clocks with NV RAM Control

DS1689/DS1693
ELAPSED TIME COUNTERS
The DS1689/DS1693 has two 32-bit elapsed time counters, which reside in bank 1 of the RTC registers.
To access these counters the DV0 bit in register A must first be set to a logical 1.
The V_CC powered elapsed time counter resides in register 54H through 57H. The LSB of this counter
resides in register 54 and the MSB is in 57H. The V_CC powered elapsed time counter runs only while the
V_CCI input is within nominal limits. The elapsed time counter is a binary counter that records the number
of seconds that have elapsed. The counter can be read or written at the user’s discretion. The V_BAT-
powered elapsed time counter resides in register 58H through 5BH. The LSB of this counter resides in
register 58 and the MSB is in 5BH.
The V_BAT powered elapsed time counter runs continually as long as the V_BAT or V_BAUX pin is within
nominal limits regardless of the condition of V_CCI. The number of seconds that have elapsed is recorded
in a binary counter and the counter can be read or written at the user’s discretion.
In a typical application, the V_BAT-powered elapsed time counter can be used to record the length of time
that has elapsed from which the equipment that contains the device was first put into service. The V_CC
powered counter can then be used to record the length of time that V_CC power is applied. These functions
can be particularly useful for warranty and maintenance information. In addition, battery life can be
predicted based on known loading factors. However, it is worth noting that a properly selected battery
should power the DS1689/DS1693 and external RAM for the useful life of most equipment.
POWER-CYCLE COUNTER
The DS1689/DS1693 has a 16-bit power-cycle counter that resides in register 5C and 5D of bank 1. The
LSB of this counter resides in 5C and the MSB is in 5D. This binary counter is incremented by one count
each time V_CCI power is applied within nominal limits. This counter can be read or written at the user’s
discretion.
23 of 36