Datasheet
Preliminary Data Sheet
BMA400
Page 33 /
Confidential
BST-BMA400-DS000-00 | Version 0.1 | November 2017 Bosch Sensortec
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Note: Specifications within this document are subject to change without notice.
Frames
The FIFO captures data in frames, which consist of a header and a payload.
Each data frame consists of a one byte header describing properties of the frame, (which data
are included in this frame) and the data itself. Beside the data frames, there are control frames,
sensortime frames and empty frames.
The header has a length of 8 bit and the following format:
Bit
7
6
5
4
3
2
1
0
Header
fh_mode<1:0>
fh_param<4:0>
0
fh_mode and fh_param<4> indicate whether the frame is a data frame (accel data), a sensortime
frame ( sensortime data) , a control frame or an empty frame (all data 0).
A data frame is composed of the said header and a set of acceleration data organized as described in
table below.
Bit
7
6
5
4
3
2
1
0
Header
fh_mode<1:0>
fh_param<4:0>
0
Data 1..7
1 .. 7 Data bytes, number depending of 12 or 8bit storage mode and number of
axes enabled.
These fh_mode and fh_parm fields are defined below
fh_mode<1:0>
Definition
fh_param <4>
fh_param <3>
fh_param <2:0>
0b10
Sensor data
frame
b0: Sensor data frame
b0: 8bit mode
b1: 12bit mode
Enabled axes
0b10
sensortime frame
b1: sensortime frame
no meaning
No meaning
0b01
Control frame
b0001
Name
fh_parm<2:0>
Bit
2
1
0
Content
z-enabled
y-enabled
x-enabled
f_param<3:0>=0b0000 is invalid for regular mode, a header of 0x80 indicates an uninitialized frame.
In a data frame, fh_param<2:0> defines which sensors axes are included in the data part of the frame.
fh_param<3> defines in which resolution – 8 or 12bit – the data are stored.
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