LIS35DE datasheet(26/39 Pages) STMICROELECTRONICS

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LIS35DE

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Doc ID 15594 Rev 1

7.2

CTRL_REG2 (21h)

SIM bit selects the SPI serial interface mode. When SIM is ‘0’ (default value) the 4-wire

interface mode is selected. The data coming from the device are sent to SDO pad. In 3-wire

interface mode output data are sent to SDA_SDI pad.

BOOT bit is used to refresh the content of internal registers stored in the flash memory

block. At the device power up the content of the flash memory block is transferred to the

internal registers related to trimming functions to permit a good behavior of the device itself.

If for any reason the content of trimming registers is changed it is sufficient to use this bit to

restore correct values. When BOOT bit is set to ‘1’ the content of internal flash is copied

inside corresponding internal registers and it is used to calibrate the device. These values

are factory trimmed and they are different for every accelerometer. They permit a good

behavior of the device and normally they have not to be changed. At the end of the boot

process the BOOT bit is set again to ‘0’.

FDS bit enables (FDS=1) or bypass (FDS=0) the high pass filter in the signal chain of the

sensor

HP_coeff[2:1]. These bits are used to configure high-pass filter cut-off frequency ft.

Table 19.

CTRL_REG2 (21h) register

SIM

BOOT

FDS

HP_FF_

WU2

HP_FF_

WU1

HP_coeff2

HP_coeff1

Table 20.

CTRL_REG2 (21h) register description

SIM

SPI Serial Interface Mode selection. Default value: 0

(0: 4-wire interface; 1: 3-wire interface)

BOOT

Reboot memory content. Default value: 0

(0: normal mode; 1: reboot memory content)

FDS

Filtered Data Selection. Default value: 0

(0: internal filter bypassed; 1: data from internal filter sent to output register)

HP FF_WU2

High Pass filter enabled for FreeFall/WakeUp # 2. Default value: 0

(0: filter bypassed; 1: filter enabled)

HP_FF_WU1

High Pass filter enabled for Free-Fall/Wake-Up #1. Default value: 0

(0: filter bypassed; 1: filter enabled)

HP_coeff2

HP_coeff1

High pass filter cut-off frequency configuration. Default value: 00

(See table below)

Table 21.

High pass filter cut-off frequency configuration

HP_coeff2,1

ft (Hz)

(DR=100 Hz)

ft (Hz)

(DR=400 Hz)

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