M41ST85W_11 STMICROELECTRONICS [STMicroelectronics], M41ST85W_11 Datasheet - Page 23

• Manufacturer Part Number: M41ST85W_11
• Description: 3.0/3.3 V I2C combination serial RTC, NVRAM supervisor and microprocessor supervisor
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

M41ST85W
3.4
Note:
Figure 15. Alarm interrupt reset waveform
Table 3.
RPT5
1
1
1
1
1
0
ACTIVE FLAG
IRQ/FT/OUT
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
M41ST85W is in the battery backup to serve as a system wake-up call.
Bits RPT5–RPT1 put the alarm in the repeat mode of operation.
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 as shown in
write '0' to the alarm date register and to RPT5–RPT1.
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.
The IRQ/FT/OUT output is cleared by a READ to the flags register. A subsequent READ of
the flags register is necessary to see that the value of the alarm flag has been reset to '0.'
The IRQ/FT/OUT pin can also be activated in the battery backup mode. The IRQ/FT/OUT
will go low if an alarm occurs and both ABE (alarm in battery backup 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 M41ST85W was in the deselect mode during
power-up.
Alarm repeat modes
RPT4
Figure 16 on page 24
0Eh
1
1
1
1
0
0
RPT3
1
1
1
0
0
0
Doc ID 7531 Rev 11
illustrates the backup mode alarm timing.
0Fh
RPT2
1
1
0
0
0
0
RPT1
1
0
0
0
0
0
Figure
Table 3
15. To disable alarm,
HIGH-Z
10h
Once per second
shows the possible
Once per minute
Once per month
Alarm setting
Once per hour
Once per year
Once per day
Clock operation
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