AN2335 Datasheet, PDF (19/40 Pages) STMicroelectronics – This document is intended to give application

AN2335
About control registers
6.2
CTRL_REG2 (21h)
Control register #2.
SIM
BOOT
--
FDS
HP
FF_WU2
HP
FF_WU1
HP coeff2
HP coeff1
SPI Serial Interface Mode selection. Default value: 0
SIM
(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)
High Pass filter enabled for FreeFall/WakeUp # 2. Default value: 0
HP FF_WU2
(0: filter bypassed; 1: filter enabled)
High Pass filter enabled for Free-Fall/Wake-Up #1. Default value: 0
HP FF_WU1
(0: filter bypassed; 1: filter enabled)
HP coeff2 High pass filter cut-off frequency configuration. Default value: 00
HP coeff1
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 was 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, they are different for every accelerometer 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 FF_WU[2:1]. These bits enable (HP FF_WU=1) or bypass (HP FF_WU=0) the high pass
filter in interrupt generation blocks.
HP coeff[2:1]. These bits are used to configure high-pass filter cut-off frequency ft
accordingly to the table given below:
HPcoeff2,1
00
01
10
11
ft (Hz)
(DR=100 Hz)
2
1
0.5
0.25
ft (Hz)
(DR=400 Hz)
8
4
2
1
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