FXLS8471Q datasheet(50/75 Pages) FREESCALE

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FXLS8471Q

Sensors

Freescale Semiconductor, Inc.

A_FFMT_SRC[a_ffmt_ea] flag can only be cleared by reading the A_FFMT_SRC register. When A_FFMT_CFG[a_ffmt_ele] = 0,

freefall or motion events are not latched

, and the A_FFMT_SRC[a_ffmt_ea] bit reflects the real-time status of the event detection.

A_FFMT_THS[a_ffmt_dbcntm] bit determines the debounce filtering behavior of the logic which sets the

A_FFMT_SRC[a_ffmt_ea] bit. See Figure 17 for details.

It is possible to enable/disable each axis used in the freefall/motion detection function by configuring bits

A_FFMT_CFG[a_ffmt_xefe], A_FFMT_CFG[a_ffmt_yefe], and A_FFMT_CFG[a_ffmt_zefe].

The freefall/motion detection function has the option to use a common 7-bit unsigned threshold for each of the X, Y, Z axes, or

individual unsigned 13-bit thresholds for each axis. When A_FFMT_THS_X_MSB[a_ffmt_ths_xyz_en] = 0, the 7-bit threshold

value stored in register 0x17 is used as a common 7-bit threshold for the X, Y, and Z axes. When a_ffmt_ths_xyz_en = 1, each

axis may be programmed with an individual 13-bit threshold (stored in the A_FFMT_X/Y/Z MSB and LSB registers).

10.8.1

A_FFMT_CFG (0x15) register

Freefall/motion configuration register.

Table 74. A_FFMT_CFG register

a_ffmt_ele

a_ffmt_oae

a_ffmt_zefe

a_ffmt_yefe

a_ffmt_xefe

—

000000

Table 75. A_FFMT_CFG bit descriptions

Field

Description

a_ffmt_ele

a_ffmt_ele denotes whether the enabled event flag will be latched in the A_FFMT_SRC register or the event flag status in the

A_FFMT_SRC will indicate the real-time status of the event. If a_ffmt_ele bit is set to a logic ‘1’, then the event flags are frozen

when the a_ffmt_ea bit gets set, and are cleared by reading the A_FFMT_SRC source register.

Default value: 0

0: Event flag latch disabled

1: Event flag latch enabled

a_ffmt_oae

a_ffmt_oae bit allows the selection between motion (logical OR combination of high-g X, Y, Z-axis event flags) and freefall

(logical AND combination of low-g X, Y, Z-axis event flags) detection.

Motion detect/freefall detect logic selection.

Default value: 0 (freefall flag)

0: Freefall flag (Logical AND combination of low-g X, Y, Z-axis event flags)

1: Motion flag (Logical OR combination of high-g X, Y, Z event flags)

a_ffmt_zefe

a_ffmt_zefe enables the detection of a high- or low-g event when the measured acceleration data on Z-axis is above/below

the threshold set in the A_FFMT_THS register. If the a_ffmt_ele bit is set to logic ‘1’ in the A_FFMT_CFG register, new event

flags are blocked from updating the A_FFMT_SRC register.

Default value: 0

0: Event detection disabled

1: Raise event flag on measured Z-axis acceleration above/below threshold.

a_ffmt_yefe

a_ffmt_yefe enables the detection of a high- or low-g event when the measured acceleration data on Y-axis is above/below

the threshold set in the A_FFMT_THS register. If the a_ffmt_ele bit is set to logic ‘1’ in the A_FFMT_CFG register, new event

flags are blocked from updating the A_FFMT_SRC register.

Default value: 0

0: Event detection disabled

1: Raise event flag on measured Y-axis acceleration above/below threshold.

a_ffmt_xefe

a_ffmt_xefe enables the detection of a high- or low-g event when the measured acceleration data on X-axis is above/below

the threshold set in the A_FFMT_THS register. If the a_ffmt_ele bit is set to logic ‘1’ in the A_FFMT_CFG register, new event

flags are blocked from updating the A_FFMT_SRC register.

Default value: 0

0: Event detection disabled

1: Raise event flag on measured X-axis acceleration above/below threshold.

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