M41T66Q6F STMicroelectronics, M41T66Q6F Datasheet - Page 19

• Manufacturer Part Number: M41T66Q6F
• Description: IC RTC SERIAL W/ALARM 16-QFN
• Manufacturer: STMicroelectronics
• Type: Clock/Calendar/Alarmr

Specifications of M41T66Q6F

• Memory Size: 16B
• Time Format: HH:MM:SS:hh (24 hr)
• Date Format: YY-MM-DD-dd
• Interface: I²C, 2-Wire Serial
• Voltage - Supply: 1.5 V ~ 4.4 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-QFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-8377-2

M41T66
3.4
Note:
Note:
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 three bits RB2-RB0 select the resolution
where:
000=1/16 second (16Hz)
001=1/4 second (4Hz)
010=1 second (1Hz)
011=4 seconds (1/4Hz) and
100 = 1 minute (1/60Hz)
Invalid combinations (101, 110, and 111) will NOT enable a watchdog time-out. Setting the
BMB4-BMB0 = 0 with any combination of RB2-RB0, other than 000, will result in an
immediate watchdog time-out.
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 M41T66
sets the WDF (watchdog flag) and generates an interrupt on the IRQ/OUTpin. The
watchdog timer can only 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, any value may be written to the watchdog register in
order to clear the IRQ/OUT pin. A value of 00h will disable the watchdog function until it is
again programmed to a new value. 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.
A WRITE to any clock register will restart the watchdog timer.
Clock operation
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