sca3060 VTI Hamlin, sca3060 Datasheet - Page 6

• Manufacturer Part Number: sca3060
• Description: 3-axis Accelerometer
• Manufacturer: VTI Hamlin

2.2.3.1
2.3 Motion Detection Mode
2.3.1
VTI Technologies Oy
www.vti.fi
Description
Overflow condition
Since acceleration data registers have no limiter, the possible overflow needs to be detected using
bits [B7, B6, B5]. If bits [B7, B6, B5] are ‘010’ (also '011') or ‘101’ (also '100'), data overflow has
occurred (see Table 1). This applies for all acceleration output registers (X_LSB … Z_MSB and
BUF_DATA).
Table 1. Overflow bit patterns in acceleration data registers (X_LSB … Z_MSB and BUF_DATA).
Byte
Bit number
Acceleration data bit
Data overflow on
positive acceleration
Data overflow on
negative
acceleration
x = ignore
In case of overflow, the output register value must be discarded. When an overflow is detected, the
bit pattern ‘0011 1111 1111 1xxx’ is used for positive accelerations and ‘1100 0000 0000 0xxx’ for
negative accelerations until a valid acceleration value is read. In Table 2 the maximum and
minimum acceleration register values that are in measuring range (for registers X_LSB … Z_MSB)
for SCA3060 are presented.
Table 2. Maximum and minimum values in the SCA3060 measuring range.
In MD mode, the ADC's data is not fed to the signal processing channel but to the MD block. It
consists of a digital band-pass filter (BPF), threshold level programmable digital comparator and a
configurable trigger function.
BPF's -3 dB low-pass frequency is 25 Hz …60 Hz and -3 dB high-pass frequency is
0.05 Hz …1 Hz. See Figure 1 below.
First positive
acceleration value
out of range
Maximum positive
acceleration value
in range
Minimum negative
acceleration value
in range
First negative
acceleration value
out of range
[mg]
dec
bin
[mg]
dec
bin
[mg]
dec
bin
[mg]
dec
bin
MSB byte
Sign
B7
0
1
SCA3060
-
2048
0100 0000 0000 0xxx
2047 mg
2047
0011 1111 1111 1xxx
-2047 mg
-204
1100 0000 0000 0xxx
-
-2048
1011 1111 1111 1xxx
Doc.Nr. 82 1150 00
d11
B6
1
0
d10
B5
0
1
B4
d9
x
x
B3
d8
x
x
B2
d7
x
x
B1
d6
x
x
B0
d5
x
x
LSB byte
B7
d4
x
x
B6
d3
x
x
B5
d2
x
x
B4
d1
x
x
SCA3060 Series
B3
d0
x
x
B2:B0
xxx
xxx
Rev B
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