m41st85w STMicroelectronics, m41st85w Datasheet - Page 23

• Manufacturer Part Number: m41st85w
• Description: 3.0/3.3v I 2c Combination Serial Rtc, Nvram Supervisor And Microprocessor Supervisor
• Manufacturer: STMicroelectronics

Note:
Figure 15. Alarm interrupt reset waveform
Table 3.
RPT5
1
1
1
1
1
0
ACTIVE FLAG
IRQ/FT/OUT
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 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 M41ST85W was in the deselect
mode during power-up.
Alarm repeat modes
RPT4
0Eh
1
1
1
1
0
0
Figure 16 on page 24
RPT3
1
1
1
0
0
0
0Fh
RPT2
1
1
0
0
0
0
illustrates the back-up mode alarm timing.
RPT1
1
0
0
0
0
0
Figure
Table 3
HIGH-Z
10h
15. To disable alarm,
Once per Second
shows the possible
Once per minute
Once per month
Alarm setting
Once per hour
Once per year
Once per day
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