M41T81S

SRAM M41T81S is a low power Serial RTC with a built-in 32.768kHz oscillator (external crystal controlled). Eight bytes of the SRAM (see Table 2., page 12) are used for the clock/calendar function and are configured in binary coded decimal (BCD) format. An additio znal 12 bytes of SRAM provide status/ control of Alarm, Watchdog and Square Wave functions. Addresses and data of M41T81S are transferred serially via a two line, bi-directional I2C interface. The built-in address register is incremented automatically after each WRITE or READ data byte.

The M41T81S 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 clock operations of M41T81S can be supplied by a small lithiumbutton 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 M41T81S is supplied in either an 8-pin SOIC or an 18-pin (MY), 300mil SOIC package which includes an embedded 32kHz crystal.

The 18-pin, embedded crystal SOIC M41T81S requires only a user-supplied battery to provide non-volatile operation.