M41T94

The M41T94 Serial TIMEKEEPER^® SRAM is a low power, 512-bit static CMOS SRAM organized as 64 words by 8 bits. A built-in 32,768 Hz oscillator (external crystal controlled) and 8 bytes of the SRAM (see Table 10, page 17)M41T94 are used for the clock/calendar function and are configured in binary coded decimal (BCD) format.

An additional 12 bytes of RAM M41T94 provide status/control of Alarm, Watchdog and Square Wave functions. Addresses and data are transferred serially via a serial SPI interface. The built-in address register is incremented automatically after each WRITE or READ data byte. The M41T94 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 M41T94 and clock operations can be supplied by a small lithium button-cell 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. Other features include a Power-On Reset as well as two additional debounced inputs (RSTIN1 and RSTIN2) M41T94 can also generate an output Reset (RST). 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 ninth clock address location controls user access to the clock information and M41T94 also stores the clock software calibration setting.