M41ST95W

The M41ST95Y/W Serial TIMEKEEPER^® SRAM is a low power, 512-bit static CMOS SRAM organized as 64 words by 8 biT. A built-in 32,768Hz oscillator (external crystal controlled) and 8 bytes of the SRAM (see Table 4., page 16) are used for the clock/calendar function and are configured in binary coded decimal (BCD) format.

An additional 12 bytes of RAM 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 M41ST95Y/W 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 buttoncell supply when a power failure occurs. Functions available to the user include a non-volatile, timeof- 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) which 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 M41ST95Y/W is supplied in a 28-lead SOIC SNAPHAT^® (MH) package (which integrates both crystal and battery in a single SNAPHAT top), or a 28-pin, 300mil SOIC package (MX) which includes an embedded 32kHz crystal.

The 28-pin, 330mil SOIC provides sockets with gold plated contacts at both ends for direct connection to a separate SNAPHAT housing containingthe battery and crystal. The unique design allows the SNAPHAT battery/crystal package to be mounted on top of the SOIC package after the completion of the surface mount process.

Insertion of the SNAPHAT housing after reflow prevents potential battery and crystal damage due to the high temperatures required for device surface- mounting. The SNAPHAT housing is also keyed to prevent reverse insertion.

The SNAPHAT SOIC and battery/crystal packages are shipped separately in plastic anti-static tubes or in Tape & Reel form. For the 28-lead SOIC, the battery/crystal package (e.g., SNAPHAT) part number is "M4TXX-BR12SH" (see Table 20., page 33).

Caution: Do not place the SNAPHAT battery/crystal top in conductive foam, as this will drain the lithium button-cell battery.

The 300mil, embedded crystal SOIC requires only a user-supplied battery to provide non-volatile operation.