L9779WD datasheet(119/170 Pages) STMICROELECTRONICS

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L9779WD

Functional description

169

Watchdog influence on power up/down management unit

The watchdog AB1 counter is increased every time the watchdog error counter is EC > 7,

which means it has an overflow. If the AB1 counter reaches the value of 7 and a further error

occurs, the system will be switched off same as it would happen in case of the already

existing PWL_EN_TIMEOUTN signal.

Watchdog influence on smart power reset

WDA has influence on the RST pin only if the WDA error counter is EC > 7 and the resulting

reset signal "WD_RST" is enabled by MSC configuration bit "INIT_WDR" in

WR_RESPTIME command.

Watchdog influence on Lsa functions (Section 6.9.1)

For LSa functions OUT1, OUT2, OUT3, OUT4 (not OUT5).

In case of an internal WDA event (e.g. the WDA error counter is EC > 4 which results in the

signal WDA_INT being set) or in case of the WDA pin being pulled low externally, the output

stages OUT1, OUT2, OUT3, OUT4 go to inactive state.

Watchdog influence on LSd functions OUT13, OUT14 (starter relay drivers)

Section 6.9.4

In case of an internal WDA event (e.g. the WDA error counter is EC > 4 which results in the

signal WDA_INT being set) or in case of the WDA pin being pulled low externally, the

OUT13 and OUT14 stages go to inactive state after the time delay THOLD if the WDA event

is still active.

In the case WDA event has switched off OUT13/OUT14 once, Thold becomes 0ms on the

next WDA event, unless OUT13/OUT14 are switched off/on or device has been reset.

Moreover, if WDA pin is Low and kept Low at power up, OUT13/OUT14 can be switched on

by the external micro, even though WDA EC ≥ 4. That is to allow external micro to control

the system especially in the case of WDA pin stuck-low. WDA status pin can be checked by

bit 3 of DIA3_REG. See also Section 6.2.2.

Watchdog influence on Ignition drivers IGN1, IGN2, IGN3, IGN4

In case of an internal WDA event (e.g. the WDA error counter is EC > 4 which results in the

signal WDA_INT being set) or in case of the WDA pin is pulled low externally, the output

stages go to inactive state.

Watchdog influence on CAN transceiver

The WDA has influence on the CAN if the MSC configuration bit CAN_TDI is set.

Once the CAN_TDI bit is set, in case of an internal WDA event (e.g. the WDA error counter

is EC > 4 which results in the signal WDA_INT being set) or in case of the WDA pin is pulled

low externally, the CAN goes to receive-only mode (Rx Only).

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