M4T32-BR12SHX STMICROELECTRONICS [STMicroelectronics], M4T32-BR12SHX Datasheet - Page 20

• Manufacturer Part Number: M4T32-BR12SHX
• Description: Serial real-time clock with 44 bytes NVRAM and reset
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

4.3
Note:
20/41
Setting alarm clock registers
Address locations 0Ah-0Eh contain the Alarm settings. 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. It can also be programmed to go off while the
M41T94 is in the battery back-up to serve as a system wake-up call.
Bits RPT5-RPT1 put the Alarm in the Repeat mode of operation.
the possible configurations. Codes not listed in the table default to the once per second
mode to quickly alert the user of an incorrect 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,
the Alarm condition activates the IRQ/FT/OUT pin.
If the address pointer is allowed to increment to the Flag register address, an Alarm
condition will not cause the Interrupt/Flag to occur until the address pointer is moved to a
different address. It should also be noted that if the last address written is the “Alarm
Seconds,” the address pointer will increment to the Flag address, causing this situation to
occur.
To disable the Alarm, write '0' to the Alarm date register and to RPT1–5. The IRQ/FT/OUT
output is cleared by a READ to the Flags register. This READ of the Flags register will also
reset the Alarm Flag (D6; register 0Fh). See
The IRQ/FT/OUT pin can also be activated in the Battery Back-up mode. The IRQ/FT/OUT
will go low if an Alarm occurs and both ABE (Alarm in Battery Back-up mode Enable) and
AFE are set. The ABE and AFE bits are reset during power-up, therefore an Alarm
generated during power-up will only set AF. The user can read the Flag register at system
boot-up to determine if an Alarm was generated while the M41T94 was in the deselect
mode during power-up.
Table 5.
RPT5
1
1
1
1
1
0
Alarm repeat mode
RPT4
1
1
1
1
0
0
Figure 12 on page 21
RPT3
1
1
1
0
0
0
Figure 11 on page
illustrates the Back-up mode Alarm timing.
RPT2
1
1
0
0
0
0
RPT1
1
0
0
0
0
0
21.
Table 5 on page 20
Once per second
Once per minute
Once per month
Alarm setting
Once per hour
Once per year
Once per day
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