MMA8452QR1 Freescale Semiconductor, MMA8452QR1 Datasheet - Page 31

• 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

register being set to 1) the event flag. In particular EA is set to a logic ‘1’ when the logical combination of acceleration events
flags specified in FF_MT_CFG register is true. This bit is used in combination with the values in INT_EN_FF_MT and
INT_CFG_FF_MT register bits to generate the freefall/motion interrupts.
defined in the FF_MT_THS register.
to the preset threshold value defined in the FF_MT_THS register.
0x17: FF_MT_THS Freefall and Motion Threshold Register
8g. Note that even when the full scale value is set to 2g or 4g the motion detects up to 8g. If the Low Noise bit is set in Register
0x2A then the maximum threshold will be limited to 4g regardless of the full scale range.
true.
as shown in
inertial event of interest is no longer true
becomes active.
impede the detection of inertial events.
Table 28. FF_MT_THS Description
Sensors
Freescale Semiconductor
Table 27. Freefall/Motion Source Description
0x17 FF_MT_THS Register (Read/Write)
This register keeps track of the acceleration event which is triggering (or has triggered, in case of ELE bit in FF_MT_CFG
An X,Y, or Z motion is true when the acceleration value of the X or Y or Z channel is higher than the preset threshold value
Conversely an X, Y, and Z low event is true when the acceleration value of the X and Y and Z channel is lower than or equal
The threshold resolution is 0.063g/LSB and the threshold register has a range of 0 to 127 counts. The maximum range is to
DBCNTM bit configures the way in which the debounce counter is reset when the inertial event of interest is momentarily not
When DBCNTM bit is a logic ‘1’, the debounce counter is cleared to 0 whenever the inertial event of interest is no longer true
Decrementing the debounce counter acts as a median enabling the system to filter out irregular spurious events which might
DBCNTM
DBCNTM
THS[6:0]
Bit 7
ZHE
ZHP
YHE
YHP
XHE
XHP
EA
Figure
Event Active Flag. Default value: 0.
0: No event flag has been asserted; 1: one or more event flag has been asserted.
See the description of the OAE bit to determine the effect of the 3-axis event flags on the EA bit.
Z Motion Flag. Default value: 0.
0: No Z Motion event detected, 1: Z Motion has been detected
This bit reads always zero if the ZEFE control bit is set to zero
Z Motion Polarity Flag. Default value: 0.
0: Z event was Positive g, 1: Z event was Negative g
This bit read always zero if the ZEFE control bit is set to zero
Y Motion Flag. Default value: 0.
0: No Y Motion event detected, 1: Y Motion has been detected
This bit read always zero if the YEFE control bit is set to zero
Y Motion Polarity Flag. Default value: 0
0: Y event detected was Positive g, 1: Y event was Negative g
This bit reads always zero if the YEFE control bit is set to zero
X Motion Flag. Default value: 0
0: No X Motion event detected, 1: X Motion has been detected
This bit reads always zero if the XEFE control bit is set to zero
X Motion Polarity Flag. Default value: 0
0: X event was Positive g, 1: X event was Negative g
This bit reads always zero if the XEFE control bit is set to zero
Debounce counter mode selection. Default value: 0.
0: increments or decrements debounce, 1: increments or clears counter.
Freefall /Motion Threshold: Default value: 000_0000.
14, (b). While the DBCNTM bit is set to logic ‘0’ the debounce counter is decremented by 1 whenever the
THS6
Bit 6
THS5
Bit 5
(Figure
14, (c)) until the debounce counter reaches 0 or the inertial event of interest
THS4
Bit 4
THS3
Bit 3
THS2
Bit 2
THS1
Bit 1
MMA8452Q
THS0
Bit 0
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