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Inertial interrupt

AN4662

Table 22: IG_SRC1(2) description

Interrupt Active. Default value: 0 (0: no interrupt has been generated; 1: one or

more interrupt requests has been generated)

Z High. Default value: 0 (0: no request; 1: ZH interrupt request has occurred)

Z Low. Default value: 0 (0: no request; 1: ZL interrupt request has occurred)

Y High. Default value: 0 (0: no request; 1: YH interrupt request has occurred)

Y Low. Default value: 0 (0: no request; 1: YL interrupt request has occurred)

X High. Default value: 0 (0: no request; 1: XH interrupt request has occurred)

X Low. Default value: 0 (0: no request; 1: XL interrupt request has occurred)

6.1

Duration

The IG_DUR1(2) register content sets the minimum duration of the interrupt event to be

recognized. Duration can also be represented as the number of consecutive samples that

have to verify the interrupt condition before generating the interrupt signal. The duration

counter starts to increase when the interrupt condition is verified and allows generating the

interrupt only when the IG_DUR1(2) content value is reached; the steps and maximum time

value depend on the selected ODR. In normal condition the duration counter is set to zero

as soon as the interrupt condition is no longer verified unless the decrement function is

enabled.

Duration time is measured in N/ODR [s], where N is the duration register content and ODR

can assume the values: 10, 50, 100, 200, 400 and 800 Hz.

Table 23: Duration LSB value in normal mode

ODR (Hz)

Duration LSB value (ms)

100

200

400

2.5

800

1.25

The duration counter allows preventing an interrupt generation in the presence of a glitch

bigger than the selected threshold.

6.1.1

Decrement function

The decrement functionality is enabled by setting the DCRM1(2) bit to “1” in CTRL7(26h)

as the interrupt condition is no longer verified, but the duration counter is not set to zero

immediately: it starts to decrease from the IG_DUR1(2) register value. If a new interrupt

condition is verified before the duration counter reaches zero, it starts to increase again

from the actual value and a new interrupt is generated when the duration counter reaches

again the IG_DUR1(2) register value.

This function allows greater reactivity on consecutive interrupt conditions.

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