DS1554

5 of 21

BATTERY LONGEVITY

The DS1554 has a lithium power source that is designed to provide energy for the clock activity, and

supply is sufficient to power the DS1554 continuously for the life of the equipment in which it is

installed. For specification purposes, the life expectancy is 10 years at 25

°C with the internal clock

expectancy of the DS1554 will be much longer than 10 years since no internal battery energy is

INTERNAL BATTERY MONITOR

The DS15543 constantly monitors the battery voltage of the internal batter. The Battery Low Flag (BLF)

bit of the Flags Register (B4 of 7FFF0h) is not writable and should always be a 0 when read. If a 1 is ever

present, an exhausted lithium energy source is indicated and both the contents of the RTC and RAM are

questionable.

POWER-ON RESET

RST

signal continues to be pulled low for a period of 40 ms to 200 ms. The power-on reset function is

independent of the RTC oscillator and thus is operational whether or not the oscillator is enabled.

CLOCK OPERATIONS

Table 2 and the following paragraphs describe the operation of RTC, alarm, and watchdog functions.