DocID13284 Rev 2 479/564
UM0404 System reset
Synchronous reset and RPD pin
Whenever the RSTIN pin is pulled low (by external hardware or as a consequence of a
Bidirectional reset), the RPD internal weak pull-down is activated. The external capacitance
(if any) on RPD pin is slowly discharged through the internal weak pull-down. If the voltage
level on RPD pin reaches the input low threshold (around 2.5V), the reset event becomes
immediately asynchronous. In case of hardware reset (short or long) the situation goes
immediately to the one illustrated in Figure 194 on page 476. There is no effect if RPD
comes again above the input threshold: the asynchronous reset is completed coherently. To
grant the normal completion of a synchronous reset, the value of the capacitance should be
big enough to maintain the voltage on RPD pin sufficient high along the duration of the
internal reset sequence.
For a Software or Watchdog reset events, an active synchronous reset is completed
regardless of the RPD status.
It is important to highlight that the signal that makes RPD status transparent under reset is
the internal RSTF
(after the noise filter).
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