Datasheet

Data Sheet
BMA456
Page 29
BST-BMA456-DS000-01 | Version 1.1 | October 2017 Bosch Sensortec
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Note: Specifications within this document are subject to change without notice.
Sample drop frames will be inserted only for transition phases after configuration changes, not for
samples dropped between sensor enable and first valid sample. For a detailed description of
configuration changes see Section 4.4, Subsection “Configuration Changes”.
FIFO Partial frame reads
When a frame is only partially read through the Register FIFO_DATA it will be repeated completely
with the next access both in headerless and in header mode. In headermode, this includes the header.
In the case of a FIFO overflow between the first partial read and the second read attempt, the frame
may be deleted.
FIFO overreads
When more data are read from the FIFO than it contains valid data, 0x8000 is returned in headerless
mode. In header mode 0x80 indicates an invalid frame.
FIFO data synchronization
All sensor data are sampled with respect to a common ODR time grid. Even if a different ODR is
selected for the acceleration and the magnetic sensor the data remains synchronized:
If a frame contains a sample from a sensor element with ODR x, then it must contain also samples of
all sensor elements with an ODR y>=x. This applies for steady state operation. In transition phases, it
is more important not to lose data, therefore exceptions are possible if the sensor elements with ODR
y>=x do not have data, e.g. due to a sensor configuration change.
FIFO Data Synchronization Scheme in the following figure illustrates the steady state and transient
operating conditions.
ACC
MAG
t
ACC
MAG
t
1/ODR_ACC
1/ODR_MAG
ACC
MAG
t
ACC enabled
ACC start-up time
Frame inconsistency
accepted during
transition phases
MAG start-up time
MAG enabled
Steady state
operation