DS1557 Maxim, DS1557 Datasheet - Page 8

• Manufacturer Part Number: DS1557
• Description: The DS1557 is a full-function, year-2000-compliant (Y2KC), real-time clock/calendar (RTC) with an RTC alarm, watchdog timer, power-on reset, battery monitor, and 512k x 8 nonvolatile static RAM
• Manufacturer: Maxim

Figure 3. Clearing IRQ Waveforms
The IRQ/FT pin can also be activated in the battery-backed mode. The IRQ/FT will go low if an alarm
occurs and both ABE and AE are set. The ABE and AE bits are cleared during the power-up transition,
however an alarm generated during power-up will set AF. Therefore, the AF bit can be read after system
power-up to determine if an alarm was generated during the power-up sequence. Figure 4 illustrates
alarm timing during the battery-backup mode and power-up states.
Figure 4. Backup Mode Alarm Waveforms
CE
1
1
=0
8
8
7FFF0h
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