AN3308 Datasheet, PDF (22/52 Pages) STMicroelectronics – This document describes the low-voltage 3-axis digital output linear MEMS accelerometer provided in an LGA package

Inertial interrupt
AN3308
Figure 7. Free-fall, wake-up interrupt generator
4(3REG
!CCEL?8
\B\A
8(%
\B\A
75
8,%
\B\A
!CCEL?9
9(%

\B\A

9,%
\B\A
&&
!CCEL?:
:(%
\B\A
:,%
).4X?#&'!/)
".W
The threshold module which is used by the system to detect any free-fall or inertial wake-up
event is defined by the INT1_THS register. The threshold value is expressed over 7 bits as
an unsigned number and is symmetrical around the zero-g level. XH (YH, ZH) is true when
the unsigned acceleration value of the X (Y, Z) channel is higher than INT1_THS. Similarly,
XL (YL, ZL) low is true when the unsigned acceleration value of the X (Y, Z) channel is lower
than INT1_THS. Refer to Figure 8 for more details.
Figure 8. FF_WU_CFG high and low
89: HIGH
89 : LOW
&ULL3CALE
4HRESHOLDMODULE
GLEVEL
0OSITIVE
ACCELERATION
89: HIGH
4HRESHOLDMODULE
&ULL3CALE
.EGATIVE
ACCELERATION
!-V
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Doc ID 18198 Rev 1