Freescale Semiconductor FRDM-FXS-MULTI 데이터 시트
FXOS8700CQ
Sensors
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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
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
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).
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).
10.9.4
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.
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
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
). When the device is operated in hybrid mode, the effective ODR is half of what is selected in
Table 88. A_FFMT_THS_Z_MSB (0x77) register
—
a_ffmt_ths_z[12:6]
0
0b000_0000
Table 89. A_FFMT_THS_Z_LSB (0x78) register
a_ffmt_ths_z[5:0]
—
—
0b00_0000
0
0
Table 90. A_FFMT_COUNT register
a_ffmt_count[7:0]
0b0000_0000
Table 91. 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.
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 High-g Region
X, Y, Z Low-g Region
Negative
Positive
Acceleration
Acceleration
(Motion OR of enabled axes)
(Freefall - AND of enabled axes)
(Motion - OR of enabled axes)