L9924L datasheet(69/84 Pages) STMICROELECTRONICS

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L9924L

SPI interface

The bits of this register are write only (WO) and their value isn’t latched: any successive

read attempt returns 0.

A write access to a locked bit must be preceded by the relevant unlock operation: if a

read/write access to any other register is done the unlock condition is lost and a write

access to a locked bit will have no effect.

12.4.11

SYSTEM OPERATION register [0x02]

By writing this register it is possible to configure the system behavior related to watchdog

and reset. The configuration bits are locked and any write access must be preceded by an

unlock operation.

Table 52. SYSTEM OPERATION register [0x02]

Bit

Reset value

Description

Reserved

SEL24V_EN (LOCKED)

Set this bit to configure 24V support. This

option is possible only if the relevant OTP

bit is set

Reserved

WDG_INIT_ENABLE (LOCKED)

0/1(1)

1. On power on reset the value of these bit is 0, on wakeup the bits maintain the last programmed values (if

any); these bits are not cleared by the SW reset command.

Write 1 to disable the initial 500 ms

watchdog timeout

WDG_FAIL_REST_uC

(LOCKED)

0/1(1)

When 0 a watchdog failure can only switch

the power stage off, when 1 a watchdog

failure switches the power stage off and

resets the microcontroller

7-5

Reserved

Apply EPONA Cfg-REGs SW

Reset (LOCKED)

0(2)

2. After a SW reset the Watchdog is also initialized and, if not previously disabled, must be programmed and

refreshed to avoid a watchdog error occurrence.

Write 1 to force a default condition (SW

RESET) corresponding to the reset status.

This command doesn't clear the content of

bits 8 and 9 and doesn't clear the content of

read and read and clear bits.

3-1

Reserved

POWER_OFF (LOCKED)(3)

The POWER_OFF command is ignored if at least one, among the enabled wake-up sources (see register

0x04) is active. It's up to the application SW ti implement the appropriate power off sequence

Writing 1 the system enters standby mode if

no key input is active.

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