MMA8452QR1 Freescale Semiconductor, MMA8452QR1 Datasheet - Page 30

• Manufacturer Part Number: MMA8452QR1
• Description: Board Mount Accelerometers LOW G 3-AXIS 12BT EX VLT
• Manufacturer: Freescale Semiconductor

Specifications of MMA8452QR1

• Sensing Axis: X, Y, Z
• Acceleration: 2 g, 4 g, 8 g
• Digital Output - Number Of Bits: 8 bit, 12 bit
• Supply Voltage (max): 3.6 V
• Supply Voltage (min): 1.95 V
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Digital Output - Bus Interface: I2C
• Shutdown: Yes
• Sensitivity: 256 count/g, 512 count/g, 1024 count/g
• Package / Case: QFN-16
• Output Type: Digital
• Rohs Compliant: Yes
• Peak Reflow Compatible (260 C): Yes
• Acceleration Range: ± 2g, ± 4g, ± 8g
• No. Of Axes: 3
• Ic Interface Type: I2C
• Sensor Case Style: QFN
• No. Of Pins: 16
• Supply Voltage Range: 1.95V To 3.6V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

0x15 FF_MT_CFG Freefall/Motion Configuration Register
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.
0x16 FF_MT_SRC Freefall/Motion Source Register
Table 26. FF_MT_CFG Description
0x16: FF_MT_SRC Freefall and Motion Source Register (Read Only)
30
0x15 FF_MT_CFG Register (Read/Write)
MMA8452Q
This is the Freefall/Motion configuration register for setting up the conditions of the freefall or motion function.
YEFE
XEFE
ZEFE
OAE
ELE
Bit 7
Bit 7
ELE
EA
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
Motion detect / Freefall detect flag selection. Default value: 0. (Freefall Flag)
0: Freefall Flag (Logical AND combination)
1: Motion Flag (Logical OR combination)
Event flag enable on Z Default value: 0.
0: event detection disabled; 1: raise event flag on measured acceleration value beyond preset threshold
Event flag enable on Y event. Default value: 0.
0: Event detection disabled; 1: raise event flag on measured acceleration value beyond preset threshold
Event flag enable on X event. Default value: 0.
0: event detection disabled; 1: raise event flag on measured acceleration value beyond preset threshold
Bit 6
Bit 6
OAE
0
X, Y, Z High g Region
X, Y, Z High g Region
X, Y, Z Low g Region
ZEFE
Bit 5
Bit 5
ZHE
Figure 13. FF_MT_CFG High and Low g Level
YEFE
Bit 4
Bit 4
ZHP
+8g
High g + Threshold (Motion)
Low g Threshold (Freefall)
High g - Threshold (Motion)
-8g
XEFE
Bit 3
Bit 3
YHE
Bit 2
Bit 2
YHP
0
Positive
Acceleration
Negative
Acceleration
Bit 1
Bit 1
XHE
Freescale Semiconductor
0
Bit 0
Bit 0
XHP
0
Sensors