Data Sheet

Sensors

32 Freescale Semiconductor

MMA8452Q

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, 0.063g/LSB. The maximum threshold is 8g. Even if the part is set to full

scale at 2g or 4g this function will still operate up to 8g. If the Low Noise bit is set in Register 0x2A the maximum threshold to be

reached is 4g.

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.

0x1F TRANSIENT_THS Register (Read/Write)

Bit

DBCNTM THS6 THS5 THS4 THS3 THS2 THS1 THS0

Table 33. TRANSIENT_THS 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

D7 D6 D5 D4 D3 D2 D1 D0

Table 34. TRANSIENT_COUNT 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

12.5 5.1 20.4 0.638 20.4 20 80 2.5 80

6.25 5.1 20.4 0.638 40.8 20 80 2.5 160

1.56 5.1 20.4 0.638 40.8 20 80 2.5 160