DS1553 64kB, Nonvolatile, Year-2000-Compliant Timekeeping RAM

9 of 20

Figure 2. Clearing

IRQ Waveforms

Figure 3. Clearing

IRQ Waveforms

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 sets 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 = Ø