m41st87w STMicroelectronics, m41st87w Datasheet - Page 33

• 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

Electronic Serial Number
The M41ST87Y/W has a unique 8-Byte lasered,
serial number with parity. This serial number is
“Read only” and is generated such that no two de-
vices will contain an identical number.
Oscillator Stop Detection
If the Oscillator Fail (OF) Bit is internally set to a '1,'
this indicates that the oscillator has either stopped,
or was stopped for some period of time and can be
used to judge the validity of the clock and date da-
ta. This bit will be set to '1' any time the oscillator
stops. The following conditions can cause the OF
Bit to be set:
– The first time power is applied (defaults to a '1'
– The voltage present on V
– The ST Bit is set to '1.'
Table 11. Century Bits Examples
Note: 1. Leap year occurs every four years (for years evenly divisible by four), except for years evenly divisible by 100. The only exceptions
Table 12. t
Note: 1. Default Setting
on power-up).
cient to support oscillation.
are those years evenly divisible by 400 (the year 2000 was a leap year, year 2100 is not).
t
rec
CB0
rec
Bit (TR)
0
0
1
1
0
0
1
Definitions
CC
or battery is insuffi-
STOP Bit (ST)
CB1
0
1
0
1
X
0
1
If the Oscillator Fail Interrupt Enable Bit (OFIE) is
set to a '1,' the IRQ/OUT pin will also be activated.
The IRQ/OUT output is cleared by resetting the
OF Bit to '0,' resetting the OFIE Bit to '0,' or the
RST output is enabled (NOT by reading the Flag
Register).
The OF Bit will remain set to '1' until written to logic
'0.' The oscillator must start and have run for at
least 4 seconds before attempting to reset the OF
Bit to '0.' This function operates both under normal
power and in battery back-up. If the trigger event
occurs during a power-down condition, this bit will
be set correctly.
Note: The ABE Bit must be set to '1' for the IRQ/
OUT pin to be activated in battery back-up.
Initial Power-on Defaults
See
Table 13., page
Leap Year?
Min
96
40
50
Yes
No
No
No
t
rec
Time
34.
M41ST87Y, M41ST87W
2000
98
Max
200
(1)
Example
2000
2100
2200
2300
(1)
Units
ms
ms
µs
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