AN2960 datasheet(20/41 Pages) STMICROELECTRONICS

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About control registers

AN2960

20/41

Doc ID 15557 Rev 1

6.2

CTRL_REG2 (21h)

Control register #2.

The 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 the SDO pad. In 3-

wire interface mode, the output data are sent to the SDA/SDI pad.

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

block. At device power-up, the content of the Flash memory block is transferred to the

internal registers related to the trimming functions, to permit good device behavior. If for any

reason the content of the trimming registers is changed, this bit can be used to restore the

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

the corresponding internal registers and used to calibrate the device. These values are

factory-trimmed, are different for every accelerometer and normally should not be changed.

At the end of the boot process, the BOOT bit is set again to ‘0’.

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

the sensor.

The HP FF_WU[2:1] bits enable (HP FF_WU=1) or bypass (HP FF_WU=0) the high-pass

filter in interrupt generation blocks.

The HP coeff[2:1] bits are used to configure the high-pass filter cut-off frequency ft,

accordingly to the following table:

SIM

BOOT

FDS

FF_WU2

FF_WU1

HP coeff2

HP coeff1

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 free-fall/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

HPcoeff2,1

ft (Hz)

(DR=100 Hz)

ft (Hz)

(DR=400 Hz)

0.5

0.25

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