Datasheet

Preliminary Data Sheet
BMA400
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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.
Wake-up Interrupt / Auto wake-up
The auto-wakeup function is part of the power management concept of the BMA400. If the wakeup
function (only available in low-power mode) changes the power mode to “normal”, the host processor
can be notified by an interrupt. This is called “wakeup interrupt”, thus, the two topics “auto wakeup”
and “wakeup interrupt” are handled together in this chapter.
The transition from Low-power to Normal mode is named “wake-up”.
Switching into Normal mode from Low-power mode can be explicitly triggered by a serial interface
command. This can also be done automatically by using the auto wakeup function.
Auto wakeup can be either timer triggered or activity triggered. Each selected condition is independent
and can be used as wake-up condition. In case more than one condition is selected, the first occurred
condition sets the BMA400 into normal mode.
The three possible triggers for wake-up from low-power mode are:
- by serial command (already described in a previous chapter)
- by timeout
- by activity
Wakeup by timeout
The source condition wkup_timeout and the timeout counter threshold value
AUTOWAKEUP_1.wakeup_timeout_thres is configured in register AUTOWAKEUP(0/1).
The wakeup_timeout_thres has 12bits for configuration of counter duration, with a resolution of
2.5ms/LSB. The maximum timeout for wake-up is 10.24s (4096*2.5ms).
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