SCA8X0/21X0/3100 Series
3.1.4 Output data conversion
3.1.4.1 2g products
+/-2g product
Bit number
SCA8x0
+1g position
-1g position
+Full-scale
-Full-scale
DOUT MSB bits(7:0)
DOUT LSB bits(7:0)
12b
12b
15
s
14
1137.8
13
568.9
12
284.4
1
0
1
0
11
142.2
1
0
1
0
10
71.1
0
1
1
9
35.6
0
1
1
8
17.8
0
1
1
7
8.89
0
6
4.44
1
5
2.22
0
4
1.11
0
0
1
3
x
x
x
x
x
2
x
x
x
x
x
1
x
x
x
x
x
0
x
x
x
x
x
[-]
[mg]
1000
-1000
2274
-2275
Bits (15:4) Bits (15:4)
[Dec]
900
-900
2047
-2048
[Hex]
384
C7C
7FF
800
0
1
0
1
0
1
1
0
1
0
1
0
1
1
0
1
0
1
1
0
0
0
0
0
0
+/-2g product
Bit number
SCA31x0/SCA21x0
+1g position
-1g position
+Full-scale *)
-Full-scale *)
DOUT MSB bits(7:0)
DOUT LSB bits(7:0)
15
s
14
4551.1
13
2275.6
12
1137.8
0
1
1
0
11
568.9
1
0
1
0
10
284.4
1
0
1
0
9
8
7
6
5
8.89
0
4
4.44
1
1
1
3
2
1
x
x
x
x
x
0
x
x
x
x
x
[-]
[mg]
1000
-1000
2274
-2275
Bits (15:2) Bits (15:2)
142.2
71.1 35.56 17.78
2.22 1.11
[Dec]
900
[Hex]
384
0
1
0
1
0
1
0
1
0
1
0
1
1
0
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
0
1
0
0
0
1
0
1
1
0
-900
2047
-2048
3C7C
7FF
3800
0
s = sign bit
x = not used/defined bit
*) = positive/negative full-scale or saturation limit of ±2 g product is 2.27 g.
In SCA8X0 acceleration bits can be converted to mg acceleration (Acc) using following equation
10
9
Acc
[
mg
]
]
=
=
[
− s ⋅211 + b14⋅210 + b13⋅29 + b12⋅28 + b11⋅27 + b10⋅26 + b9⋅25 + b8⋅24 + b7⋅23 + b6⋅22 + b5⋅2 + b4
]
and in SCA21X0/SCA31X0
13
12
11
10
9
8
⎡
⎢
⎤
⎥
− s ⋅2 + b14⋅2 + b13⋅2 + b12⋅2 + b11⋅2 + b10⋅2
10
9
,
Acc mg
[
+ b9⋅27 + b8⋅26 + b7 ⋅25 + b6⋅24 + b5⋅23 + b4⋅22 + b3⋅2 + b2
⎢
⎥
⎣
⎦
where bits are defined according to following table.
Acceleration MSB-register: Address 5'hex / 7'hex / 9'hex
Acceleration LSB-register: Address 4'hex / 6'hex / 8'hex
DO7
b15
DO6
b14
DO5
b13
DO4
b12
DO3
b11
DO2
b10
DO1
b9
DO0
b8
DO7
b7
DO6
b6
DO5
b5
DO4
b4
DO3
b3
DO2
b2
DO1
b1
DO0
b0
In data output registers of SCA21X0/SCA31X0 there is reserved room for different g-ranges. To
make sure that same software works with different product types it is recommended to use
bits(15:2) for data conversion. If dynamic output range of product does not require bits b14 or b13
they include copy of sign bit b15.
If self-test (checksum, STC, STS) alarms it sets ST bit in SPI frame and forces output data to value
7FFF'hex (checksum fail) or to value FFFF'hex (STC/STS alarm).
In SCA21X0/SCA31X0 there is also possible to use 1-extra lsb bit (b1) for calculation to improve
resolution. In that case acceleration bits can be converted to mg acceleration (Acc) using following
equation
14
13
12
11
10
9
8
⎡
⎢
⎤
⎥
− s ⋅2 + b14⋅2 + b13⋅2 + b12⋅2 + b11⋅2 + b10⋅2 + b9⋅2
+ b8⋅27 + b7⋅26 + b6⋅25 + b5⋅24 + b4⋅23 + b3⋅22 + b2⋅2 + b1
10
.
Acc
[
mg
]
=
18
⎢
⎥
⎣
⎦
VTI Technologies Oy
www.vti.fi
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Doc. Nr. 82 694 00 C
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