Datasheet

M41T66 Description
Doc ID 15108 Rev 2 5/34
1 Description
The M41T66 is a low-power serial real-time clock (RTC) with a built-in 32.768 kHz oscillator
(external crystal controlled). Eight registers are used for the clock/calendar function and are
configured in binary coded decimal (BCD) format. An additional 8 registers provide
status/control of alarm, square wave, calibration, and watchdog functions. Addresses and
data are transferred serially via a two line, bidirectional I
2
C interface. The built-in address
register is incremented automatically after each WRITE or READ data byte.
Functions available to the user include a time-of-day clock/calendar, alarm interrupts,
programmable square wave output, and watchdog output. The eight clock address locations
contain the century, year, month, date, day, hour, minute, second and tenths/hundredths of a
second in 24-hour BCD format. Corrections for 28-, 29- (leap year), 30- and 31-day months
are made automatically.
The M41T66 is supplied in a 16-pin QFN.
Figure 1. M41T66 logic diagram
1. Open drain
2. Defaults to 32 KHz on power-up
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