M41T94(2003) 查看數據表（PDF） - STMicroelectronics
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M41T94 Datasheet PDF : 31 Pages
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M41T94
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. It can also be pro-
grammed to go off while the M41T94 is in the bat-
tery back-up to serve as a system wake-up call.
Bits RPT5-RPT1 put the alarm in the repeat mode
of operation. Table 11, page 18 shows the possi-
ble configurations. Codes not listed in the table de-
fault 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 condi-
tion activates the IRQ/FT/OUT pin.
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.
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 Figure 15,
page 18.
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 Bat-
tery 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. Figure 16, page 19 illus-
trates the back-up mode alarm timing.
Table 11. Alarm Repeat Mode
RPT5
RPT4
1
1
1
1
1
1
1
1
1
0
0
0
RPT3
1
1
1
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
Figure 15. Alarm Interrupt Reset Waveforms
0Eh
0Fh
ACTIVE FLAG
IRQ/FT/OUT
10h
HIGH-Z
AI03664
18/31
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