SPC584BX datasheet(37/142 Pages) STMICROELECTRONICS

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DS11701 Rev 4

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SPC584Bx

Electrical characteristics

4.9

Reset pad (PORST) electrical characteristics

The device implements dedicated bidirectional reset pins as below specified. PORST pin

does not require active control. It is possible to implement an external pull-up to ensure

correct reset exit sequence. Recommended value is 4.7 K

.

Figure 5. Startup

reset requirements

Figure 6 describes device behavior depending on supply signal on PORST:

PORST low pulse has too low amplitude: it is filtered by input buffer hysteresis. Device

remains in current state.

PORST low pulse has too short duration: it is filtered by low pass filter. Device remains

in current state.

PORST low pulse is generating a reset:

PORST low but initially filtered during at least WFRST. Device remains initially in

current state.

PORST potentially filtered until WNFRST. Device state is unknown. It may either

be reset or remains in current state depending on extra condition (temperature,

voltage, device).

PORST asserted for longer than WNFRST. Device is under reset.

VIL

VDD

PORST

VIH

device start-up phase

VDD_POR

PORST driven low by

device reset

forced by external circuitry

PORST undriven

device reset by

internal power-on reset

SPC584BX Datasheet(PDF) 37 Page - STMicroelectronics