M41ST87WMX6 STMicroelectronics, M41ST87WMX6 Datasheet - Page 6

• Manufacturer Part Number: M41ST87WMX6
• Description: IC SUPERVISOR RTC 160X8 28-SOIC
• Manufacturer: STMicroelectronics
• Type: Clock/Calendar/Supervisorr

Specifications of M41ST87WMX6

• Memory Size: 160B
• Time Format: HH:MM:SS:hh (24 hr)
• Date Format: YY-MM-DD-dd
• Interface: I²C, 2-Wire Serial
• Voltage - Supply: 2.7 V ~ 3.6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 28-SOIC, 28-SOH (8.48mm Width)
• Function: Clock/Calendar/Alarm/Timer Interrupt
• Rtc Memory Size: 160 Byte
• Supply Voltage (max): 3.6 V
• Supply Voltage (min): 2.7 V
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT
• Rtc Bus Interface: Serial (2-Wire, I2C)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-5370-5; M41ST87WMX6

Description
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Description
The M41ST87Y/W secure serial RTC and NVRAM supervisor 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 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 finally 128 bytes of user RAM are
also provided. Addresses and data are transferred serially via a two line, bidirectional I
interface. The built-in address 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 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, tamper detection, 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), 30 and 31 day months are
made automatically.
Security features
Two fully independent tamper detection Inputs allow monitoring of multiple locations within
the system. User programmable bits provide both normally open and normally closed switch
monitoring. Time stamping of the tamper event is automatically provided. There is also an
option allowing data stored in either internal memory (128 bytes), and/or external memory to
be cleared, protecting sensitive information in the event tampering occurs. By embedding
the 32 kHz crystal in the SOX28 package, the clock is completely isolated from external
tampering. An oscillator fail bit (OF) is also provided to ensure correct operation of the
oscillator.
The M41ST87Y/W is supplied in a 28-pin, 300 mil SOIC package (MX) which includes an
embedded 32 kHz crystal and a 20-pin SSOP package (SS) for use with an external crystal.
The SOIC and SSOP packages are shipped in plastic anti-static tubes or in tape & reel form.
The 300 mil, embedded crystal SOIC requires only a user-supplied battery to provide non-
volatile operation.
Doc ID 9497 Rev 9
M41ST87Y, M41ST87W
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