DS1554WP-120IND Maxim Integrated Products, DS1554WP-120IND Datasheet - Page 9

• Manufacturer Part Number: DS1554WP-120IND
• Description: Real Time Clock
• Manufacturer: Maxim Integrated Products

Specifications of DS1554WP-120IND

• Function: Clock, Calendar, NV Timekeeping RAM, Watchdog Timekeeper
• Rtc Memory Size: 32768 B
• Supply Voltage (max): 3.63 V
• Supply Voltage (min): 2.97 V
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Rtc Bus Interface: Parallel
• Package / Case: PowerCap
• Time Format: HH:MM:SS
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Table 3. Alarm Mask Bits
When the RTC Register values match Alarm Register settings, the Alarm Flag bit (AF) is set to a 1. If
Alarm Flag Enable (AE) is also set to a 1, the alarm condition activates the IRQ/FT pin. The IRQ/FT
signal is cleared by a read or write to the Flags Register (Address 7FF0h) as shown in Figure 2 and 3.
When CE is active, the IRQ/FT signal may be cleared by having the address stable for as short as 15 ns
and either OE or WE active, but is not guaranteed to be cleared unless t
also cleared by a read or write to the Flags Register but the flag will not change states until the end of the
read/write cycle and the IRQ/FT signal has been cleared.
Figure 2. Clearing IRQ Waveforms
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.
AM4
1
1
1
1
0
CE,
AM3
CE=0
1
1
1
0
0
0V
AM2
1
1
0
0
0
AM1
1
0
0
0
0
ALARM RATE
Once per second
When seconds match
When minutes and seconds match
When hours, minutes, and seconds match
When date, hours, minutes, and seconds match
DS1554 256k, Nonvolatile, Y2K-Compliant Timekeeping RAM
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RC
is fulfilled. The alarm flag is