AN3342 datasheet(10/39 Pages) STMICROELECTRONICS

10 / 39 page

Reset control

AN3342

10/39

Doc ID 18461 Rev 3

Reset control

4.1

Reset management overview

The reset pin is a 3.3 V bidirectional I/O (supplied by VDDIO). After startup it can be

programmed by software to be used as a general purpose output.

Its output buffer driving capability is fixed to IolMIN = 2 mA @ 0.45 V in the 1.65 V to 3.6 V

range which includes a ~40 k pull-up. Output buffer is reduced to the n-channel MOSFET

(NMOS). The receiver includes a glitch filter, whereas the output buffer includes a 20 µs

delay.

There are many reset sources, including:

●

External reset through the NRST pin

●

Power-on reset (POR): During power-on, the POR keeps the device under reset until

the supply voltage (VDD) reach the right voltage level.

●

Independent watchdog reset (IWDG)

●

Window watchdog reset (WWDG), featuring also software reset.

●

SWIM reset: An external device connected to the SWIM interface can request the

SWIM block to generate a microcontroller reset.

●

Illegal opcode reset: If a code to be executed does not correspond to any opcode or

prebyte value, a reset is generated.

Figure 3 shows a simplified functional I/O reset schematic.

Figure 3.

Reset management

4.1.1

Output characteristics

●

A valid pulse on the pin is guaranteed with a

 20 ns pulse duration on the internal

output buffer.

●

After a valid pulse is recognized, a pulse on the pin of at least 20 µs is guaranteed

starting from the falling edge of A (output of the OR between the different reset

sources).

RPU

VDD_IO

Pulse

generator

(min 20 µs)

System reset

Filter

100 nF

External

reset circuit

NRST

MS18949V2

Illegal op code reset

SWIM reset

POR reset

IWDG/WWDG/software reset

Delay

STM8TL5xxx

(typ 40 k

Ω)

AN3342 Datasheet(PDF) 10 Page - STMicroelectronics

AN3342 Datasheet(HTML) 10 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39

Datasheet Download

Link URL