Datasheet
Sensors
NXP Semiconductors 33
MMA8452Q
When the EA bit gets set while ELE = 1, all other status bits get frozen at their current state. By reading the TRANSIENT_SRC
register, all bits get cleared.
0x1F: TRANSIENT_THS register
The transient threshold register sets the threshold limit for the detection of the transient acceleration. The value in the
TRANSIENT_THS register corresponds to a g value which is compared against the values of high-pass filtered data. If the high-
pass filtered acceleration value exceeds the threshold limit, an event flag is raised and the interrupt is generated if enabled.
The threshold THS[6:0] is a 7-bit unsigned number, 0.063 g/LSB. The maximum threshold is 8 g. Even if the part is set to full
scale at 2 g or 4 g this function will still operate up to 8 g. If the low-noise bit is set in register 0x2A, the maximum threshold to be
reached is 4 g.
Note: If configuring the transient detection threshold for less than 1 g, the high-pass filter will need some settling time. The settling
time will vary depending on selected ODR, high-pass frequency cutoff and threshold. For more information, please refer to NXP
application note AN4071.
0x20: TRANSIENT_COUNT
The TRANSIENT_COUNT sets the minimum number of debounce counts continuously matching the condition where the
unsigned value of high-pass filtered data is greater than the user specified value of TRANSIENT_THS.
The time step for the transient detection debounce counter is set by the value of the system ODR and the oversampling mode.
XTRANSE
X-transient event. Default value: 0.
0: No interrupt, 1: X-transient acceleration greater than the value of TRANSIENT_THS event has occurred
X_Trans_Pol
Polarity of X-transient event that triggered interrupt. Default value: 0.
0: X event was positive g, 1: X event was negative g
0x1F: TRANSIENT_THS register (read/write)
Bit
7
Bit
6
Bit
5
Bit
4
Bit
3
Bit
2
Bit
1
Bit
0
DBCNTM THS6 THS5 THS4 THS3 THS2 THS1 THS0
Table 33. TRANSIENT_THS description
Field Description
DBCNTM
Debounce counter mode selection. Default value: 0. 0: increments or decrements debounce; 1: increments or clears counter.
THS[6:0]
Transient threshold: Default value: 000_0000.
0x20: TRANSIENT_COUNT register (read/write)
Bit
7
Bit
6
Bit
5
Bit
4
Bit
3
Bit
2
Bit
1
Bit
0
D7 D6 D5 D4 D3 D2 D1 D0
Table 34. TRANSIENT_COUNT description
Field Description
D[7:0]
Count value. Default
value:
0000_0000
.
Table 35. TRANSIENT_COUNT relationship with the ODR
ODR (Hz)
Max time range (s) Time step (ms)
Normal LPLN HighRes LP Normal LPLN HighRes LP
800 0.319 0.319 0.319 0.319 1.25 1.25 1.25 1.25
400 0.638 0.638 0.638 0.638 2.5 2.5 2.5 2.5
200 1.28 1.28 0.638 1.28 5 5 2.5 5
100 2.55 2.55 0.638 2.55 10 10 2.5 10
50 5.1 5.1 0.638 5.1 20 20 2.5 20
Table 32. TRANSIENT_SRC description (continued)
Field Description