m41t64 STMicroelectronics, m41t64 Datasheet - Page 20

• Manufacturer Part Number: m41t64
• Description: Serial Access Real-time Clock With Alarms
• Manufacturer: STMicroelectronics

M41T62/63/64/65
Setting Alarm Clock Registers
Address locations 0Ah-0Eh contain the alarm set-
tings. The alarm can be configured to go off at a
prescribed time on a specific month, date, hour,
minute, or second, or repeat every year, month,
day, hour, minute, or second. Bits RPT5–RPT1
put the alarm in the repeat mode of operation.
ble 7., page 20
Codes not listed in the table default to the once per
second mode to quickly alert the user of an incor-
rect alarm setting.
When the clock information matches the alarm
clock settings based on the match criteria defined
by RPT5–RPT1, the AF (Alarm Flag) is set. If AFE
(Alarm Flag Enable) is also set (M41T62/65), the
alarm condition activates the IRQ/OUT or IRQ/FT/
OUT pin. To disable the alarm, write '0' to the
Alarm Date Register and to RPT5–RPT1.
Figure 24. Alarm Interrupt Reset Waveform
Table 7. Alarm Repeat Modes
20/33
RPT5
1
1
1
1
1
0
IRQ/OUT or
IRQ/FT/OUT
ALARM FLAG BIT (AF)
shows the possible configurations.
RPT4
1
1
1
1
0
0
0Eh
RPT3
1
1
1
0
0
0
RPT2
1
1
0
0
0
0
Ta-
0Fh
Note: If the address pointer is allowed to incre-
ment to the Flag Register address, an alarm con-
dition will not cause the Interrupt/Flag to occur until
the address pointer is moved to a different ad-
dress. It should also be noted that if the last ad-
dress written is the “Alarm Seconds,” the address
pointer will increment to the Flag address, causing
this situation to occur.
The IRQ output is cleared by a READ to the Flags
Register as shown in
sequent READ of the Flags Register is necessary
to see that the value of the Alarm Flag has been
reset to '0.'
RPT1
1
0
0
0
0
0
Figure 24., page
Once per Second
Once per Minute
Once per Month
Alarm Setting
Once per Hour
Once per Year
Once per Day
HIGH-Z
00h
AI08898
20. A sub-