HTS221 datasheet(14/33 Pages) STMICROELECTRONICS

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Digital interfaces

HTS221

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Digital interfaces

The registers embedded in the HTS221 may be accessed through both the I²C and SPI

3-wire serial interfaces.

The serial interfaces are mapped onto the same pins.To select the I²C interface, the CS line

must be tied high (i.e. connected to VDD) or unconnected (internal pull-up); to select the SPI

interface, the CS line must be tied low (i.e. connected to GND).

5.1

I2C serial interface (CS = HIGH or unconnected CS)

The HTS221 I²C is a bus slave. The I²C is employed to write data into registers whose

content can also be read back.

The relevant I²C terminology is provided in Table 9.

There are two signals associated with the I²C bus: the serial clock line (SCL) and the serial

data line (SDA). The latter is a bi-directional line used for sending and receiving the data

to/from the interface. Both lines must be connected to VDD through pull-up resistors.

The I²C interface is compliant with fast mode (400 kHz) I²C standards as well as with normal

mode.

Table 8. Serial interface pin description

Pin name

Pin description

I²C/SPI mode selection

1: SPI idle mode / I²C communication enabled

0: SPI communication mode / I²C disabled)

SCL/SPC

I²C serial clock (SCL)

SPI serial clock (SPC)

SDA/SDI/SDO

I²C serial data (SDA)

3-wire SPI serial data input /output (SDI/SDO)

Table 9. I2C terminology

Term

Description

Transmitter

The device which sends data to the bus

Receiver

The device which receives data from the bus

Master

The device which initiates a transfer, generates clock signals and terminates a

transfer

Slave

The device addressed by the master

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