DS1553 Maxim, DS1553 Datasheet - Page 8

• Manufacturer Part Number: DS1553
• Description: The DS1553 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 "8k x 8 nonvolatile static RAM (NV SRAM)
• Manufacturer: Maxim

USING THE CLOCK ALARM
The alarm settings and control for the DS1553 reside within registers 1FF2h–1FF5h. Register 1FF6h
contains two alarm-enable bits: Alarm Enable (AE) and Alarm in Backup Enable (ABE). The AE and
ABE bits must be set as described below for the
condition.
The alarm can be programmed to activate on a specific day of the month or repeat every day, hour,
minute, or second. It can also be programmed to go off while the DS1553 is in the battery-backed state of
operation to serve as a system wakeup. Alarm mask bits AM1–AM4 control the alarm mode. Table 3
shows the possible settings. Configurations not listed in the table default to the once-per-second mode to
notify the user of an incorrect alarm setting.
Table 3. Alarm Mask Bits
When the RTC register values match Alarm register settings, the Alarm Flag bit (AF) is set to 1. If the
Alarm Flag Enable (AE) is also set to 1, the alarm condition activates the
is cleared by a read or write to the Flags register (Address 1FF0h) as shown in Figures 2 and 3. When
is active, the
cleared by a read or write to the Flags register, but the flag does not change states until the end of the
read/write cycle and the
OE
AM4
or
1
1
1
1
0
WE
active, but it is not guaranteed to be cleared unless t
IRQ
AM3
1
1
1
0
0
/FT signal may be cleared by having the address stable for as short as 15ns and either
IRQ
AM2
1
1
0
0
0
/FT signal has been cleared.
AM1
1
0
0
0
0
Once per second
When seconds match
When minutes and seconds match
When hours, minutes, and seconds match
When date, hours, minutes, and seconds match
8 of 20
IRQ
/FT output to be activated for a matched alarm
RC
ALARM RATE
is fulfilled. The alarm flag is also
IRQ
/FT pin. The
IRQ
/FT signal
CE