CMA3000-D0X Datasheet, PDF (15/35 Pages) VTI technologies – 3-axis accelerometer

CMA3000-D0X Series
Address: 09h
Register name: MDTHR, Motion detection threshold value register
Bits
Mode
Initial
Value
Name Description
7
0
Reserved
6:0
RW
8h MDTHR[6:0] Motion detection threshold level absolute value. See
detailed bit level weighting in Table 5 (bits [6:0])
Table 5. Bit level description in [mg] for motion detection threshold of CMA3000-D01.
Range G_RANGE
8g
0
x=not used bit
B7 B6 B5 B4 B3 B2 B1
B0
x 4571 2286 1142 571 286 143 1/14 = 71 mg
Address: 0Ah
Register name: MDFFTMR, Motion and free fall detection time register
Bits Mode ^{Initial Value}
Name
Description
7:4
RW
3h
MDTMR[3:0] ^{Motion detection timer bits}
3:0
RW
3h
FFTMR [3:0] Free fall detection timer bits
The LSB bit weighting for MDTMR and FFTMR bits are converted to seconds by using the currently
configured CMA3000 output data rate (ODR), as follows:
MDTMR_LSB[sec] = 1 / ODR[Hz], and
FFTMR_LSB[sec] = 1 / ODR[Hz]
Were the ODR is the currently configured CMA3000 output data rate, which is defined by MODE
bits (bits [3:1] in CTRL register). An example for CMA3000-D01 timer bit weighting is presented in
Table 6 below.
Table 6. An example for CMA3000-D01 MDTMR and FFTMR bit level descriptions in [ms].
Timer
Register bit number
MDTMR
FFTMR
B7
B6
B5
B4
B3
B2
B1
B0
Timer bit number
CMA3000-D01,
MODE bits x10
ODR: 400Hz
CMA3000-D01,
MODE bits x01
ODR: 100Hz
CMA3000-D01,
MODE bits 100
ODR: 10Hz
x=not used bit
MDTMR MDTMR MDTMR MDTMR
b3
b2
B1
b0
x
x
x
x
FFTMR
b3
20
FFTMR
b2
10
FFTMR
B1
FFTMR
b0
5
1/400s =
2,5 ms
x
x
x
x
80
40
20
1/100s =
10 ms
x
400
200
1/10s =
100 ms
x
x
x
x
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