M41ST87WMX6F STMICROELECTRONICS [STMicroelectronics], M41ST87WMX6F Datasheet - Page 37

• Manufacturer Part Number: M41ST87WMX6F
• Description: 5.0 V and 3.3/3.0 V secure serial RTC and NVRAM supervisor with tamper detection and 128 bytes of clearable NVRAM
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

M41ST87Y, M41ST87W
3.6
Note:
3.7
Note:
3.8
Note:
Full-time 32 kHz square wave output
The M41ST87Y/W offers the user a special 32kHz square wave function which defaults to
output on the F
'0'). This function is available within one second (typ) of initial power-up and can only be
disabled by setting the 32 kE bit to '0' or the ST bit to '1.' If not used, the F
disconnected and allowed to float.
The F
Power-on reset
The M41ST87Y/W 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.
A power-on reset will result in resetting the following control bits to '0': OFIE, AFE, ABE,
SQWE, FT, WDS, BMB0-BMB4, RB0, RB1, TIE1, and TIE2 (see
Reset inputs (RSTIN1 & RSTIN2)
The M41ST87Y/W provides two independent inputs which can generate an output reset.
The function of these resets is identical to a reset generated by a power cycle.
Figure 26
t
V
triggers on the rising edge.
RSTIN2 is available only in the SOX28 (MX) package.
Figure 26. RSTIN1 & RSTIN2 timing waveforms
R2
PFD
CC
will not generate a reset condition. RSTIN1 and RSTIN2 are each internally pulled up to
through a 100 kΩ resistor. Note that RSTIN1 triggers on the falling edge while RSTIN2
(max). The RST pin is an open drain output and an appropriate pull-up resistor should
32k
RSTIN1
RSTIN2
RST
pin is an open drain which requires an external pull-up resistor.
illustrate the AC reset characteristics of this function. Pulses shorter than t
32k
pin (pin 21) as long as V
t R1
Doc ID 9497 Rev 8
CC
CC
t rec
. When V
≥ V
Hi-Z
SO
t R2
, and the oscillator is running (ST bit =
CC
falls to the power fail detect trip
t rec
Table 13 on page
rec
32k
after V
Clock operation
Hi-Z
AI07072
pin should be
Table 10
CC
41).
passes
R1
37/52
and
and