FXLS8471Q Datasheet, PDF (50/75 Pages) Freescale Semiconductor, Inc – Linear Accelerometer

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
—
—
—
0
0
0
0
0
0
0
0
Table 75. A_FFMT_CFG bit descriptions
Field
a_ffmt_ele
a_ffmt_oae
a_ffmt_zefe
a_ffmt_yefe
a_ffmt_xefe
Description
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 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 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 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 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.
FXLS8471Q
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