L9300 datasheet(85/182 Pages) STMICROELECTRONICS

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Q&A Watchdog

14.1

Q&A watchdog functional description

ASIC and Microcontroller exchange Queries and Answers on a defined timing base.

An internal Watchdog logic is implemented to inhibit load actuation such as to send Reset signal.

A second switch-off path, as shown in Figure 52. Bidirectional Timing check evolution, is provided to allow the

Micro to force the switch off the actuation channels.

Figure 50. WD block diagram

Deglitch filter

SPI

Watchdog

Logic

Fault Counter

Logic

Actuation Enable

Loads

Configuration

WATCHDOG

EN_DR

WD_RST

(WD_CNT)

GADG0408171041PS

14.1.1

Timing

Two modes of timing checks are provided:

•

Monodirectional: Timing check based only on Answers. Microcontroller must send answers on a defined

time window

•

Bidirectional: Timings are bidirectionally checked. ASIC must receive queries on a defined time window.

Microcontroller must send answers on a defined time window

The selection between Mono and Bidirectional mode is possible through WD_REQ_CHECK_EN SPI register.

Default configuration is Monodirectional mode. Both the Mono and Bidirectional modes require the same Q/A

procedure to be controlled by the µC but:

•

in Monodirectional mode the Query can be sent in the whole timing windows between 2 Answers. Only the

timings between 2 consecutive answers must respect the defined timing window

•

in Bidirectional mode both the Request and the Answer must be sent on a predefined timing interval.

In case time windows are not respected an error is generated.

L9300

Q&A Watchdog

DS12258 - Rev 4

page 85/182

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