M41ST85W_11 STMICROELECTRONICS [STMicroelectronics], M41ST85W_11 Datasheet - Page 25

• Manufacturer Part Number: M41ST85W_11
• Description: 3.0/3.3 V I2C combination serial RTC, NVRAM supervisor and microprocessor supervisor
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

M41ST85W
3.6
3.7
pin. This will also disable the watchdog function until it is again programmed correctly. A
READ of the flags register will reset the watchdog flag (bit D7; register 0Fh).
The watchdog function is automatically disabled upon power-up and the watchdog register
is cleared. If the watchdog function is set to output to the IRQ/FT/OUT pin and the frequency
test function is activated, the watchdog function prevails and the frequency test function is
denied.
Square wave output
The M41ST85W offers the user a programmable square wave function which is output on
the SQW pin. RS3-RS0 bits located in 13h establish the square wave output frequency.
These frequencies are listed in
completed, the SQW pin can be turned on and off under software control with the square
wave enable bit (SQWE) located in register 0Ah.
Table 4.
Power-on reset
The M41ST85W continuously monitors V
point, the RST pulls low (open drain) and remains low on power-up for t
V
be chosen to control rise time.
PFD
(max). The RST pin is an open drain output and an appropriate pull-up resistor should
RS3
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
Square wave output frequency
RS2
Square wave bits
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
Doc ID 7531 Rev 11
Table
RS1
4. Once the selection of the SQW frequency has been
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
CC
. When V
RS0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
CC
falls to the power fail detect trip
Frequency
32.768
8.192
4.096
2.048
1.024
None
512
256
128
64
32
16
8
4
2
1
Square wave
rec
after V
Clock operation
CC
Units
kHz
kHz
kHz
kHz
kHz
Hz
Hz
Hz
Hz
Hz
Hz
Hz
Hz
Hz
Hz
–
passes
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