M41T81M6TR 查看數據表（PDF） - STMicroelectronics

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M41T81M6TR

SERIAL ACCESS RTC WITH ALARMS

STMicroelectronics 

M41T81

SUMMARY DESCRIPTION

The M41T81 Serial Access TIMEKEEPER®

SRAM is a low power Serial RTC with a built-in

32.768 KHz oscillator (external crystal controlled).

Eight bytes of the SRAM (see Table 10, page 16)

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

functions. Addresses and data are transferred se-

rially via a two line, bi-directional I2C interface. The

built-in address register is incremented automati-

cally 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 fail-

ure 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 in-

terrupts, Watchdog Timer and programmable

Square Wave output. The eight clock address lo-

cations 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 either an 8-pin SOIC or

an 18-pin (MY) or 28-pin (MX), 300mil SOIC pack-

age which includes an embedded 32kHz crystal.

The 8-pin and 28-pin, embedded crystal SOIC re-

quires only a user-supplied battery to provide non-

volatile operation.

Figure 4. Logic Diagram

VCC VBAT

XI(1)

XO(1)

SCL

SDA

M41T81

IRQ/FT/OUT/SQW

VSS

Note: 1. For SO8 package only.

AI04613

Table 1. Signal Names

XI(1)

Oscillator Input

XO(1)

Oscillator Output

IRQ/OUT/

FT/SQW

Interrupt / Output Driver / Frequency

Test / Square Wave (Open Drain)

SDA

SCL

Serial Data Input/Output

Serial Clock Input

VBAT

Battery Supply Voltage

VCC

Supply Voltage

VSS

Ground

Note: 1. For SO8 package only.

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