AN2381 datasheet(29/47 Pages) STMICROELECTRONICS

29 / 47 page

AN2381

Registers Description

29/47

5.4

Free-Fall and Wake-Up Registers

The following sections describes the registers that are involved in the generation of the

interrupt signal associated to the inertial wake-up and free-fall events.

5.4.1

HP_FILTER_RESET (23h)

Dummy register. A read at this address set the content of the internal High-Pass filter to the

actual X, Y and Z acceleration values.

5.4.2

FF_WU_CFG (30h)

Free-fall and wake-up configuration register.

AOI bit allows to select between Wake-Up (OR combination of interrupt events) and Free-

Fall (AND combination of interrupt events) detection

LIR defines whether the configured interrupt event has to be latched by the device once it

has happened. In order to clear the request and the related source reg (FF_WU_SRC) it is

necessary to perform a reading at the dummy register FF_WU_ACK reg.

AOI

LIR

ZHIE

ZLIE

YHIE

YLIE

XHIE

XLIE

AOI

And/Or combination of Interrupt events. Default value: 0

(0: OR combination of interrupt events; 1: AND combination of interrupt events)

LIR

Latch Interrupt request into FF_WU_SRC register with the FF_WU_SRC register

cleared by reading FF_WU_ACK register. Default value: 0

(0: interrupt request not latched; 1: interrupt request latched)

ZHIE

Enable interrupt generation on Z high event. Default value: 0