MMA8652FC datasheet(44/65 Pages) NXP

44 / 65 page

MMA8652FC

Sensors

Freescale Semiconductor, Inc.

6.9.3

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).

6.9.4

0x20 TRANSIENT_COUNT register

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.

Table 62. 0x1F TRANSIENT_THS register (Read/Write)

Back to Register Address Map

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 63. TRANSIENT_THS register

Bit(s)

Field

Description

Notes

DBCNTM

Debounce counter mode selection

0 Increments or decrements debounce (default)

1 Increments or clears counter

6–0

THS[6:0]

Transient Threshold

A 7-bit unsigned number, with 0.063 g/LSB.

The maximum threshold is ±8 g.

000_0000 (default)

Even if the part is set to full scale at ±2 g (or ±4 g), this

function will still operate up to ±8 g.

Table 64. 0x20 TRANSIENT_COUNT register (Read/Write)

Back to Register Address Map

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Table 65. TRANSIENT_COUNT register

Bit(s)

Field

Description

7–0

D[7:0]

Count value

0000_0000 (default)

Table 66. TRANSIENT_COUNT relationship with the ODR

ODR (Hz)

Max Time Range (s)

Time Step (ms)

Normal

LPLN

HighRes

Normal

LPLN

HighRes

800

0.319

1.25

400

0.638

2.5

200

1.28

0.638

1.28

2.5

100

2.55

0.638

2.55

2.5

5.1

0.638

5.1

2.5

12.5

5.1

20.4

0.638

20.4

2.5

6.25

5.1

20.4

0.638

40.8

2.5

160

1.56

5.1

20.4

0.638

40.8

2.5

160

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