AN4650 datasheet(38/102 Pages) STMICROELECTRONICS

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Interrupt generation

AN4650

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DocID027415 Rev 1



INT2_INACT_STATE: Inactivity interrupt on INT2.



INT2_SINGLE_TAP: Single-tap interrupt on INT2.



INT2_WU: Wake-up interrupt on INT2.



INT2_FF: Free-fall interrupt on INT2.



INT2_DOUBLE_TAP: Double-tap interrupt on INT2.



INT2_6D: 6D detection interrupt on INT2.



INT2_TILT: Tilt interrupt on INT2.



INT2_IRON: Soft-iron / hard-iron interrupt on INT2.

If multiple interrupt signals are routed on the same pin (INTx), the logic level of this pin is the

“OR” combination of the selected interrupt signals. In order to know which event has

generated the interrupt condition, the related source registers have to be read:

WAKE_UP_SRC, D6D_SRC, TAP_SRC and FUNC_SRC.

The INT2_on_INT1 pin of CTRL4_C register allows driving all the enabled interrupt signals

in logic “OR” on the INT1 pin (by setting this bit to 1). When this bit is set to 0, the interrupt

signals are divided between the INT1 and INT2 pins.

4.2

Free-fall interrupt

Free-fall detection refers to a specific register configuration that allows recognizing when the

device is in free-fall: the acceleration measured along all the axes goes to zero. In a real

case a “free-fall zone” is defined around the zero-g level where all the accelerations are

small enough to generate the interrupt. Configurable threshold and duration parameters are

associated to free-fall event detection: the threshold parameter defines the free-fall zone

amplitude; the duration parameter defines the minimum duration of the free-fall interrupt

event to be recognized (Figure 11).

Figure 11. Free-fall interrupt

Table 27. MD2_CFG register

INT2_

INACT_

STATE

INT2_

SINGLE_

TAP

INT2_

DOUBLE_

TAP

INT2_

TILT

INT2_

IRON

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