Datasheet

Data Sheet
BMA456
Page 114
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.
6.6. SPI and I²C Access Restrictions
In order to allow for the correct internal synchronization of data written to the BMA456, certain access
restrictions apply for consecutive write accesses or a write/read sequence through the SPI as well as
I2C interface. The required waiting period depends on whether the device is operating in normal mode
or other modes.
As illustrated in the figure below, an interface idle time of at least 2 µs is required following a write
operation when the device operates in normal mode. In suspend mode an interface idle time of least
1000 µs is required.
Post-Write Access Timing Constraints
6.7. Auxiliary Interface
The BMA456 allows attaching an external sensor (MAG-sensor) to a BMA456 via the auxiliary
interface. The connection diagrams for the auxiliary interface are depicted in the chapter 7.3. The
timings of the secondary I2C interface are the same as for the primary I2C interface, see chapter 6.5.
BM423 acts as a master of the secondary interface, controls the data acquisition of the MAG-sensor
(slave of the secondary interface) and presents the data to the application processor (AP) in the user
registers of the BMA456 through the primary interface. No external pull-up resistors need to be
connected, since an internal pull-up can be configured in the BMA456 (default value: internal pull-up
is off, please contact your regional sales representative if you want to use this functionality). No
additional I2C master or slave devices must be attached to the magnetometer interfaces.
The BMA456 autonomously reads out the sensor data from BMM150 without intervention of the AP
and stores the data in its data registers (per default) and FIFO (see Register
FIFO_CONFIG_1.fifo_aux_en). The initial setup of the BMM150 after power-on is done through
indirect addressing in the BMA456. From a system perspective the initialization for BMM150 when
attached to BMA456 should be possible within 100ms.
More information about the usage of Auxiliary Interface can be found in chapter 4.8.
X-after-Write
Register Update Period
(> 2us / 450us)
Write-Operation X-Operation