FXLS8471Q datasheet(53/75 Pages) FREESCALE

53 / 75 page

FXLS8471Q

Sensors

Freescale Semiconductor, Inc.

Figure 16. A_FFMT_THS high and low-g level

A_FFMT_THS contains the unsigned 7-bit threshold value used by the freefall/motion detection functional block and is used to

detect either low-g (freefall) or high-g (motion) events depending on the setting of G_FFMT_CFG[f_ffmt_oae]. If g_ffmt_oae = 0,

the event is detected when the absolute value of all the enabled axes are below the threshold value. When g_ffmt_oae = 1, the

event is detected when the absolute value of any of the enabled axes is above the threshold value (see Figure 16 for an

illustration of the freefall/motion event detection thresholds). If A_FFMT_THS_X_MSB[a_ffmt_ths_xyz_en] = 1, the behavior is

identical, except that each axis may be programmed with an individual 13-bit threshold (stored in the A_FFMT_X/Y/Z MSB and

LSB registers).

10.8.4

A_FFMT_COUNT (0x18) register

Debounce count register for freefall/motion detection events

This register sets the number of debounce counts for acceleration sample data matching the user-programmed conditions for

either a freefall or motion detection event required before the interrupt is triggered.

When the internal debounce counter reaches the A_FFMT_COUNT value a freefall/motion event flag is set. The debounce

counter will never increase beyond the A_FFMT_COUNT value. The time step used for the debounce sample count depends on

the ODR chosen (see Table 89).

Table 85. A_FFMT_THS_Z_MSB (0x77) register

—

a_ffmt_ths_z[12:6]

7’b0000000

Table 86. A_FFMT_THS_Z_LSB (0x78) register

a_ffmt_ths_z[5:0]

—

6’b000000

Table 87. A_FFMT_COUNT register

a_ffmt_count[7:0]

8’b00000000

Table 88. A_FFMT_COUNT bit description

Field

Description

a_ffmt_count[7:0]

a_ffmt_count defines the minimum number of debounce sample counts required for the detection of a freefall or motion

event. A_FFMT_THS[ffmt_dbcntm] determines the behavior of the counter when the condition of interest is momentarily

not true.

+Full Scale

High-g Positive Threshold

Low-g Threshold

High-g Negative Threshold

-Full Scale

X, Y, Z High-g Region

X, Y, Z Low-g Region

Negative

Positive

Acceleration

(Motion OR of enabled axes)

(Freefall - AND of enabled axes)

(Motion - OR of enabled axes)

FXLS8471Q Datasheet(PDF) 53 Page - Freescale Semiconductor, Inc

FXLS8471Q Datasheet(HTML) 53 Page - Freescale Semiconductor, Inc

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75

Datasheet Download

Link URL