参数资料
型号: M41T81M6TR
厂商: STMICROELECTRONICS
元件分类: 时钟/数据恢复及定时提取
英文描述: 1 TIMER(S), REAL TIME CLOCK, PDSO8
封装: 0.150 INCH, PLASTIC, SO-8
文件页数: 7/27页
文件大小: 388K
代理商: M41T81M6TR
15/27
M41T81
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 M41T81 is in the bat-
tery back-up mode to serve as a system wake-up
call.
Bits RPT5-RPT1 put the alarm in the repeat mode
of operation. Table 3., page 16 shows 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 (and SQWE is '0.'),
the alarm condition activates the IRQ/FT/OUT/
SQW 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.
The IRQ/FT/OUT/SQW output is cleared by a
READ to the Flags Register as shown in Figure
13. 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/SQW pin can also be activated
in the battery back-up mode. The IRQ/FT/OUT/
SQW will go low if an alarm occurs and both ABE
(Alarm in Battery Back-up Mode Enable) and AFE
are set. Figure 14 illustrates the back-up mode
alarm timing.
Figure 13. Alarm Interrupt Reset Waveform
Figure 14. Back-up Mode Alarm Waveform
IRQ/FT/OUT/SQW
ACTIVE FLAG
0Fh
0Eh
10h
HIGH-Z
AI04617
VCC
IRQ/FT/OUT/SQW
ABE and AFE Bits
AF Bit in Flags
Register
HIGH-Z
VSO
trec
AI05663
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