M41T81

Summary description

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Summary description

The M41T81 is a low power Serial RTC with a built-in 32.768kHz oscillator (external crystal

controlled). Eight bytes of the SRAM (see Table 2: Clock register map on page 14) are used

for the clock/calendar function and are configured in binary coded decimal (BCD) format. An

additional 12 bytes of SRAM provide status/control of Alarm, Watchdog and Square Wave

interface. The built-in address register is incremented automatically after each WRITE or

READ data byte.

The M41T81 has a built-in power sense circuit which detects power failures and

automatically switches to the battery supply when a power failure occurs. The energy

needed to sustain the SRAM and clock operations can be supplied by a small lithium button

supply when a power failure occurs.

Functions available to the user include a non-volatile, time-of-day clock/calendar, Alarm

interrupts, Watchdog Timer and programmable Square Wave 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 -

valid until year 2100), 30 and 31 day months are made automatically.

The M41T81 is supplied in an 8-pin SOIC.

Figure 1.

Logic diagram

SCL

M41T81

SDA

IRQ/FT/OUT/SQW

XI

XO

AI04613