BMA400 datasheet(29/121 Pages) BOSCH

29 / 121 page

Bosch Sensortec | BMA400 Data sheet

29 | 121

Modifications reserved | Data subject to change without notice

Document number: BST-BMA400-DS000-13 Revision_2.2_012025

FIFO overflow behavior

A FIFO overflow occurs if the FIFO is full and a new data is to be written to the FIFO. FIFO full means

free space is less than maximum frame length of 9 bytes. The largest frame is 7 bytes long, however

each time FIFO is written (at the end of the measurement), 9 bytes can be written to the FIFO in total,

consisting of 2 frames: one with the measurement results (maximum of 7 bytes), and configuration

change frame consisting of 2 bytes. The definition of the full interrupt uses 9 bytes limit to give the host

system time to react to it before the FIFO overflows.

In case of overflow the FIFO can either stop recording data or overwrite the oldest data. The behavior

is controlled by register fifo_stop_on_full.

Streaming mode, fifo_stop_on_full = ’0’: if the new frame does not fit inside the remaining free space

in the FIFO RAM, FIFO will repeatedly delete the oldest frame until it creates enough space for the

new one.

FIFO stop-on-full mode, fifo_stop_on_full = ’1’: The newest frame is discarded.

Normal operation resumes if the FIFO full condition no longer persists.

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

Header

fh_mode<1:0>

fh_param<4:0>

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

Header

fh_mode<1:0>

fh_param<4:0>

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

b00100

BMA400 Datasheet(PDF) 29 Page - Bosch Sensortec GmbH

BMA400 Datasheet(HTML) 29 Page - Bosch Sensortec GmbH

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL