M41ST87WMX6 STMicroelectronics, M41ST87WMX6 Datasheet - Page 39

• 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

M41ST87Y, M41ST87W
3.11
3.12
Note:
3.13
Century bits
These two bits will increment in a binary fashion at the turn of the century, and handle leap
years correctly. Refer to
years register (07h), and should be set accordingly. For example, for the year 2100, they
would be set to 1 (D7 = 0 and D6 = 1), and for the year 2300, they would be set to 3 (D7 = 1
and D6 = 1). Once set, they will increment every 100 years. Provided they are set as
described above, the date register (05h) will properly manage leap day at the turn of any
century. Leap day does not occur in turn-of-century years except for those which are
multiples of 400. Thus, with CB1 and CB0 properly set, the device will omit leap day from
the appropriate turn-of-century years.
Table 11.
1. Leap year occurs every four years (for years evenly divisible by four), except for years evenly divisible by
Output driver pin
When the TIE bit, OFIE bit, AFE bit, and watchdog register are not set to generate an
interrupt, the IRQ/OUT pin becomes an output driver that reflects the contents of D7 of the
control register. In other words, when D7 (OUT bit) is a '0,' then the IRQ/OUT pin will be
driven low. With the ABE bit set to '1,' the OUT pin will continue to be driven low in battery
backup.
The IRQ/OUT pin is an open drain which requires an external pull-up resistor.
Battery low warning
The M41ST87Y/W automatically performs battery voltage monitoring upon power-up and at
factory-programmed time intervals of approximately 24 hours. The battery low (BL) bit, bit
D4 of flags register 0Fh, will be set if the battery voltage is found to be less than
approximately 2.5 V. The BL bit will remain set until completion of battery replacement and
subsequent battery low monitoring tests, either during the next power-up sequence or the
next scheduled 24-hour interval.
If a battery low is generated during a power-up sequence, this indicates that the battery is
below approximately 2.5 volts and may not be able to maintain data integrity in the SRAM.
Data should be considered suspect and verified as correct. A fresh battery should be
installed.
If a battery low indication is generated during the 24-hour interval check, this indicates that
the battery is near end of life. However, data is not compromised due to the fact that a
nominal V
battery back-up mode, the battery should be replaced. The battery should be replaced while
V
CC
100. The only exceptions are those years evenly divisible by 400 (the year 2000 was a leap year, year
2100 is not).
is applied to the device.
CB1
CC
0
0
1
1
Century bits examples
is supplied. In order to ensure data integrity during subsequent periods of
Table
11. These bits represent the next higher order bits of the
Doc ID 9497 Rev 9
CB0
0
1
0
1
Leap year?
Yes
No
No
No
Clock operation
Example
2000
2100
2200
2300
(1)
39/54