m41st87w STMicroelectronics, m41st87w Datasheet - Page 5

• Manufacturer Part Number: m41st87w
• Description: 5.0, 3.3, Or 3.0v, 1280 Bit 160 X8 Secure Serial Rtc And Nvram Supervisor With Tamper Detection
• Manufacturer: STMicroelectronics

SUMMARY DESCRIPTION
The M41ST87Y/W Serial TIMEKEEPER
troller SRAM is a low power 1280-bit, static CMOS
SRAM organized as 160 bytes by 8 bits. A built-in
32.768 kHz oscillator (internal crystal-controlled)
and 8 bytes of the SRAM (see
are used for the clock/calendar function and are
configured in binary coded decimal (BCD) format.
An additional 11 bytes of RAM provide calibration,
status/control of Alarm, Watchdog, Tamper, and
Square Wave functions. 8 bytes of ROM and final-
ly 128 bytes of User RAM are also provided. Ad-
dresses and data are transferred serially via a two
line, bi-directional I
dress register is incremented automatically after
each WRITE or READ data byte. The M41ST87Y/
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 op-
erations can be supplied by a small lithium button-
cell supply when a power failure occurs.
Functions available to the user include a non-vol-
atile, time-of-day clock/calendar, Alarm interrupts,
Tamper Detection, Watchdog Timer, and pro-
grammable Square Wave output. Other features
include a Power-On Reset as well as two addition-
al debounced inputs (RSTIN1 and RSTIN2) which
can also generate an output Reset (RST). The
eight clock address locations contain the century,
2
C interface. The built-in ad-
Table 7., page
®
/Con-
25)
year, month, date, day, hour, minute, second and
tenths/hundredths of a second in 24 hour BCD for-
mat. Corrections for 28, 29 (leap year), 30 and 31
day months are made automatically.
Security Features
Two fully independent Tamper Detection Inputs al-
low monitoring of multiple locations within the sys-
tem. Programmable bits provide both, “Normally
Open” and “Normally Closed” switch monitoring.
Time Stamping of the tamper event is automatical-
ly provided. There is also an option allowing data
stored in either internal memory (128 bytes), and/
or external memory to be cleared, protecting sen-
sitive information in the event tampering occurs.
By embedding the 32kHz crystal in the package,
the clock is completely isolated from external tam-
pering. An Oscillator Fail Bit (OF) is also provided
to ensure correct operation of the oscillator.
The M41ST87Y/W is supplied in a 28-pin, 300mil
SOIC package (MX) which includes an embedded
32kHz crystal.
The SOIC package is shipped in plastic anti-static
tubes or in Tape & Reel form.
The 300mil, embedded crystal SOIC requires only
a user-supplied battery to provide non-volatile op-
eration.
M41ST87Y, M41ST87W
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