L9912TR datasheet(72/84 Pages) STMICROELECTRONICS

72 / 84 page

SPI interface

L9912

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DocID029639 Rev 2

When set, the receiver stage of the corresponding pin is disabled and cannot neither detect

a wakeup condition nor change the relevant status bit in register 0x11 (IGNIT_KEY,

LHC_KEY, L_KEY); the output stage, when present, isn’t affected by the disable bit and is

always enabled.

For example, if a wake-up by lamp is disabled, the system is still able to drive the lamp

output but cannot exit from stand-by because of a L-input transition and the pin status isn't

available on register 0x11, but can drive the lamp output.

In these conditions, if the application needs, after wake-up, to use the L-input it has to clear

the relevant wake-up disable bit.

The following sequence can be applied:



… exit from stand by (caused by some other source); in this condition the L-interface

cannot receive any protocol but the lamp, if present, can be properly handled



Clear the WKUP_SOURCE_L_DISABLE bit in order to enable the interface



Wait for the interface activation time (~100 µs)



Run the application



Set the WKUP_SOURCE_L_DISABLE bit in order to disable the interface to generate

a wakeup



Enter standby

The stand-by exit by phase cannot be disabled. Disabling wake-up sources contributes to

reduce the stand-by power consumption

DFM_polarity

1: the output PWM signal begins with

an active pulse and is followed by the

inactive interval

0: the output PWM signal begins with

the inactive interval followed by the

active pulse

5-4

DFM_DRV_SEL

DFM output configuration:

0. DFM output disabled

1. Low side driver enabled

2. High side driver enabled

3. Push-pull enabled

3-0

DFM_freq

0x0F

DFM signal frequency from 100 Hz to

400Hz with 25 Hz steps:

– 0000: 100 Hz

– 0001: 125 Hz

–…

– 1011: 375 Hz

– 1100-1110: 400 Hz

– 1111: DFM OFF (default)

Table 55. WAKE-UP sources and DFM GEN setup register [0x04] (continued)

Bit

Reset value

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