MMA8452Q
Sensors
26
Freescale Semiconductor, Inc.
0x15: FF_MT_CFG Freefall/Motion Configuration Register
This is the Freefall/Motion configuration register for setting up the conditions of the freefall or motion function.
OAE
bit allows the selection between Motion (logical OR combination) and Freefall (logical AND combination) detection.
ELE
denotes whether the enabled event flag will to be latched in the FF_MT_SRC register or the event flag status in the
FF_MT_SRC will indicate the real-time status of the event. If ELE bit is set to a logic ‘1’, then the event flags are frozen when the
EA bit gets set, and are cleared by reading the FF_MT_SRC source register.
ZHFE, YEFE, XEFE
enable the detection of a motion or freefall event when the measured acceleration data on X, Y, Z channel
is beyond the threshold set in FF_MT_THS register. If the ELE bit is set to logic ‘1’ in the FF_MT_CFG register new event flags
are blocked from updating the FF_MT_SRC register.
FF_MT_THS
is the threshold register used to detect freefall motion events. The unsigned 7-bit
FF_MT_THS
threshold register
holds the threshold for the freefall detection where the magnitude of the X and Y and Z acceleration values is lower or equal than
the threshold value. Conversely, the
FF_MT_THS
also holds the threshold for the motion detection where the magnitude of the
X or Y or Z acceleration value is higher than the threshold value.
Figure 12. FF_MT_CFG High- and Low-g Level
0x16: FF_MT_SRC Freefall/Motion Source Register
0x15: FF_MT_CFG Register (Read/Write)
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
ELE
OAE
ZEFE
YEFE
XEFE
0
0
0
Table 26. FF_MT_CFG Description
ELE
Event Latch Enable: Event flags are latched into FF_MT_SRC register. Reading of the FF_MT_SRC register clears the event
flag EA and all FF_MT_SRC bits. Default value: 0.
0: Event flag latch disabled; 1: event flag latch enabled
OAE
Motion detect / Freefall detect flag selection. Default value: 0. (Freefall Flag)
0: Freefall Flag (Logical AND combination)
1: Motion Flag (Logical OR combination)
ZEFE
Event flag enable on Z Default value: 0.
0: event detection disabled; 1: raise event flag on measured acceleration value beyond preset threshold
YEFE
Event flag enable on Y event. Default value: 0.
0: Event detection disabled; 1: raise event flag on measured acceleration value beyond preset threshold
XEFE
Event flag enable on X event. Default value: 0.
0: event detection disabled; 1: raise event flag on measured acceleration value beyond preset threshold
0x16: FF_MT_SRC Freefall and Motion Source Register (Read Only)
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
EA
0
ZHE
ZHP
YHE
YHP
XHE
XHP
+8g
High-g + Threshold (Motion)
Low-g Threshold (Freefall)
High-g - Threshold (Motion)
-8g
X, Y, Z High-g Region
X, Y, Z High-g Region
X, Y, Z Low-g Region
Negative
Positive
Acceleration
Acceleration
