M41ST84W View Datasheet(PDF) - STMicroelectronics
Part Name
Description
Manufacturer
M41ST84W Datasheet PDF : 34 Pages
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M41ST84W
Clock operation
Note:
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.
The IRQ/FT/OUT output is cleared by a READ to the flags register as shown in Figure 14. 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 M41ST84W was in the deselect mode during
power-up. Figure 15 on page 22 illustrates the backup mode alarm timing.
Figure 14. Alarm interrupt reset waveform
0Eh
0Fh
10h
ACTIVE FLAG
IRQ/FT/OUT
HIGH-Z
AI03664
Table 4.
RPT5
1
1
1
1
1
0
Alarm repeat modes
RPT4
RPT3
1
1
1
1
1
1
1
0
0
0
0
0
RPT2
1
1
0
0
0
0
RPT1
1
0
0
0
0
0
Alarm setting
Once per second
Once per minute
Once per hour
Once per day
Once per month
Once per year
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