Datasheet

Preliminary Data Sheet
BMA400
Page 30 /
Confidential
BST-BMA400-DS000-00 | Version 0.1 | November 2017 Bosch Sensortec
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BOSCH and the symbol are registered trademarks of Robert Bosch GmbH, Germany.
Note: Specifications within this document are subject to change without notice.
Sensor Time
The BMA400 has an integrated sensor timer. The sensor time can be used for synchronization
purposes between the external MCU and the sensor.
The sensor timer counts the clock cycles generated by the system clock which is always running in
low-power and normal modes. Sensor timer is inactive in sleep mode and reset when entering the
sleep mode. Counter values are stored in registers SENSOR_TIME(0/1/2).
The sensor timer has a resolution of 21 bits stored in 3 bytes. For compatibility with other sensors that
use faster counters with 25.6 kHz, the lower three bits of the counter (sensor_time<2:0>) are always
0. Thus, the lowest significant bit of the counter is sensor_time<3>.
After the timer has reached the maximum value, the counter resets to zero.
The sensortime is synchronized with the data capturing in the data register and the FIFO. The
sensortime supports multiple seconds of sample counting and a sub-millisecond resolution.
Burst reads on the registers SENSORTIME_0 to SENSORTIME_2 deliver always consistent values,
i.e. the value of the register does not change during the burst read.
Bit m in
sensor_time
23
22
21
…
8
7
6
5
4
3
Resolution
[ms]
327.68
163.84
81.92
…
10
5
2.5
1.250
0.625
0.3125
Update rate
[Hz]
0.0031
0.0061
0.012
…
100
200
400
800
1600
3200
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Confidential and under NDA