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M41T81M6F 参数 Datasheet PDF下载

M41T81M6F图片预览
型号: M41T81M6F
PDF下载: 下载PDF文件 查看货源
内容描述: 报警串行访问实时时钟 [Serial access Real-Time Clock with alarm]
分类和应用: 时钟
文件页数/大小: 30 页 / 303 K
品牌: STMICROELECTRONICS [ ST ]
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Clock operation  
Figure 13. Back-up mode alarm waveform  
M41T81  
V
CC  
V
SO  
trec  
ABE and AFE Bits  
AF Bit in Flags  
Register  
IRQ/FT/OUT/SQW  
HIGH-Z  
AI05663  
Table 3.  
RPT5  
Alarm repeat modes  
RPT4  
RPT3  
RPT2  
RPT1  
Alarm setting  
1
1
1
1
1
0
1
1
1
1
0
0
1
1
1
0
0
0
1
1
0
0
0
0
1
0
0
0
0
0
Once per second  
Once per minute  
Once per hour  
Once per day  
Once per month  
Once per year  
3.5  
Watchdog timer  
The watchdog timer can be used to detect an out-of-control microprocessor. The user  
programs the watchdog timer by setting the desired amount of time-out into the Watchdog  
Register, address 09h. Bits BMB4-BMB0 store a binary multiplier and the two lower order  
bits RB1-RB0 select the resolution, where 00 = 1/16 second, 01 = 1/4 second, 10 = 1  
second, and 11 = 4 seconds. The amount of time-out is then determined to be the  
multiplication of the five-bit multiplier value with the resolution. (For example: writing  
00001110 in the Watchdog Register = 3*1, or 3 seconds). If the processor does not reset  
the timer within the specified period, the M41T81 sets the WDF (Watchdog Flag) and  
generates a watchdog interrupt.  
The watchdog timer can be reset by having the microprocessor perform a WRITE of the  
Watchdog Register. The time-out period then starts over.  
Should the watchdog timer time-out, a value of 00h needs to be written to the Watchdog  
Register in order to clear the IRQ/FT/OUT/SQW pin. This will also disable the watchdog  
function until it is again programmed correctly. A READ of the Flags Register will reset the  
Watchdog Flag (Bit D7; Register 0Fh).  
The watchdog function is automatically disabled upon power-up and the Watchdog Register  
is cleared. If the watchdog function is set, the frequency test function is activated, and the  
SQWE Bit is '0,' the watchdog function prevails and the frequency test function is denied.  
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