L9779WD datasheet(114/170 Pages) STMICROELECTRONICS

114 / 170 page

Functional description

L9779WD

114/170

DocID027452 Rev 5

ERROR COUNTER (EC) and reactions, AB1 COUNTER (AB1_CNT) and

generation of the monitoring module reset

Various actions are initiated for specific counter states of the ERROR COUNTER EC. The

counter reset state is 6.

For ERROR COUNTER (EC) > 4, <WDA_INT> is set to '1', thus activating the open-drain

output [WDA] that is low-active.

Shutdown in an error state in "power-latch"

If the ERROR COUNTER reaches the value ‘7’ and a further error occurs the AB1

COUNTER AB1_CNT is incremented by one during a sequencer-run.

The state "EC = 7 and a further error occurs" is also called ERROR COUNTER overflow

("EC" > 7).

If ERROR COUNTER > 4 AND a soft-reset is detected then the COUNTER AB1_CNT is

also incremented by one. The counter AB1_CNT is a 3 bit counter.

Behaviour of AB1_CNT:

asynchronous reset to "000" with RST_UV

synchronous reset to "000" IF <WDA_INT> = LOW (EC < 5)

IF (AB1_CNT < 7) AND ((sequencer-run AND ‘EC’ > 7) OR soft-reset) THEN

AB1_CNT = AB1_CNT + 1

ELSE unchanged.

The counter cannot be decremented and can be only reset to "000" by an active RST_UV

signal (asynchronous) or <WDA_INT> = '0' (synchronous).

The signal AB1 becomes active '1' when AB1_CNT = ‘111’ and a further error is detected

when the sequencer runs or when AB1_CNT = ‘111’ and a soft-reset is detected.

In "power-latch", the active AB1 signal causes a shut-down of the main relay and the voltage

regulators. This function ensures a secure shutdown of the system in an error state of the

µC in "power-latch".

Signal AB1 is set to '0' again only when <WDA_INT> = '0'.

Table 50. Error counter

ERROR

COUNTER

0 ... 4

6 ... 7

Over flow EC > 7

WDA_INT

low – i.e. ‘0’

high – i.e. ‘1’

[WDA]

inactive – i.e. ‘1’

active – i.e. ‘0’

AB1-

COUNTER

unchanged

incremented

by 1

AB1

low – i.e. ‘0’

unchanged

AB1_CNT < 7: low

AB1_CNT 6

 7: low

AB1_CNT 7

 7: high

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