L9965P datasheet(58/104 Pages) STMICROELECTRONICS

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3.8.1

Measurement trigger modes

The ADC supports three different conversion execution modes:

•

On-Demand, triggered by MCU writing ADC_CONV_CMD bit equal to 1 and configuring the input channel

with the AMUX_CONF bit field in the same command frame (see the Table 31):

–

This type of request does not move the FSM to DIAG state.

–

Results of the on-demand ADC conversions are available in the ADC_CONV_RESULT register when

ADC_CONV_RDY bit is set to 1.

–

If the ADC is just busy, the ADC_BUSY bit is set to 1.

•

Cyclically:

–

In full-power mode (CWUP = 1, static), the diagnostic routine runs every tDIAG_ROUTINE_PERIOD. The

voltage ADC is involved in some diagnostic steps (if such steps are enabled).

–

In low-power mode (periodic CWUP pulses), the diagnostic routine is executed at every wake

‑up.

–

These types of requests move the FSM to DIAG state.

•

Asynchronously:

–

If the FSM moves to the ARM state, the ADC is used for post-deployment resistance measurement if

selected as the FIRE_GOOD source.

–

The result of this conversion is reported in the RES_MEAS_POST register.

Conflict between multiple triggers is managed as follows:

•

If the FSM is in DIAG state (either triggered by CWUP in low-power mode or triggered by the MCU in full-

power mode), on-demand triggers are discarded.

Note:

When in low-power mode, the FSM moves to DIAG upon cyclic powerups. Hence, the cyclic execution of

the diagnostic routine is guaranteed by design.

•

If an on-demand conversion is being performed, the cyclic execution of the diagnostic routine is skipped

and it will be performed upon the next useful trigger period.

•

In any case, if the FSM moves to the ARM state, any ongoing conversion is interrupted and the ADC will be

set up for post-deployment resistance measurement. This deployment trigger has the highest priority.

Table 31. ADC input channel selection for on-demand conversions

AMUX_CONF

Channel

000

PS vs PGND

001

PF vs PGND

010

PR vs PGND

011

PF vs PR (high resolution - pre deployment)

100

PF vs PR (low resolution - post deployment)

101

ERBST vs GNDx

110

VRCM vs PGND

111

Not used

The ADC LSB is rescaled according to the selected channel and to the diagnostic steps.

L9965P

Functional description

DS14702 - Rev 4

page 58/104

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