M41T81MY6 STMICROELECTRONICS [STMicroelectronics], M41T81MY6 Datasheet - Page 4

• Manufacturer Part Number: M41T81MY6
• Description: Serial Access Real-Time Clock with Alarms
• Manufacturer: STMICROELECTRONICS [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 I
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
Figure 4. Logic Diagram
Note: 1. For SO8 package only.
4/28
XO
SDA
XI
SCL
(1)
(1)
V CC
M41T81
V SS
V BAT
IRQ/FT/OUT/SQW
2
C interface. The
AI04613
®
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.
Table 1. Signal Names
Note: 1. For SO8 package only.
IRQ/OUT/
FT/SQW
XO
V
SDA
XI
SCL
V
V
BAT
CC
SS
(1)
(1)
Oscillator Input
Oscillator Output
Interrupt / Output Driver / Frequency
Test / Square Wave (Open Drain)
Serial Data Input/Output
Serial Clock Input
Battery Supply Voltage
Supply Voltage
Ground