MMA8452Q

Sensors

Freescale Semiconductor, Inc.

33

0x23 - 0x25: PULSE_THSX, Y, Z Pulse Threshold for X, Y & Z Registers

The pulse threshold can be set separately for the X, Y and Z axes. The PULSE_THSX, PULSE_THSY and PULSE_THSZ

registers define the threshold which is used by the system to start the pulse detection procedure.

The threshold values range from 1 to 127 with steps of 0.63g/LSB at a fixed 8g acceleration range, thus the minimum

resolution is always fixed at 0.063g/LSB. If the Low-Noise bit in Register 0x2A is set then the maximum threshold will be 4g. The

PULSE_THSX, PULSE_THSY and PULSE_THSZ registers define the threshold which is used by the system to start the pulse

detection procedure. The threshold value is expressed over 7-bits as an unsigned number.

0x26: PULSE_TMLT Pulse Time Window 1 Register

The bits TMLT7 through TMLT0 define the maximum time interval that can elapse between the start of the acceleration on the

selected axis exceeding the specified threshold and the end when the acceleration on the selected axis must go below the

specified threshold to be considered a valid pulse.

The minimum time step for the pulse time limit is defined in Table 42 and Table 43. Maximum time for a given ODR and

Oversampling mode is the time step pulse multiplied by 255. The time steps available are dependent on the Oversampling mode

and whether the Pulse Low-Pass Filter option is enabled or not. The Pulse Low-Pass Filter is set in Register 0x0F.

0x23: PULSE_THSX Register (Read/Write)

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

0

THSX6

THSX5

THSX4

THSX3

THSX2

THSX1

THSX0

Table 38. PULSE_THSX Description

THSX[6:0]

Pulse Threshold on X-axis. Default value: 000_0000.

0x24: PULSE_THSY Register (Read/Write)

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

0

THSY6

THSY5

THSY4

THSY3

THSY2

THSY1

THSY0

Table 39. PULSE_THSY Description

THSY[6:0]

Pulse Threshold on Y-axis. Default value: 000_0000.

0x25: PULSE_THSZ Register (Read/Write)

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

0

THSZ6

THSZ5

THSZ4

THSZ3

THSZ2

THSZ1

THSZ0

Table 40. PULSE_THSZ Description

THSZ[6:0]

Pulse Threshold on Z-axis. Default value: 000_0000.

0x26: PULSE_TMLT Register (Read/Write)

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

TMLT7

TMLT6

TMLT5

TMLT4

TMLT3

TMLT2

TMLT1

TMLT0

Table 41. PULSE_TMLT Description

TMLT[7:0]

Pulse Time Limit. Default value: 0000_0000.

Table 42. Time Step for PULSE Time Limit (Reg 0x0F) Pulse_LPF_EN = 1

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