LSM320HAY30 datasheet(20/42 Pages) STMICROELECTRONICS

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Digital interfaces

LSM320HAY30

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Doc ID 16917 Rev 1

Digital interfaces

The registers embedded in the LSM320HAY30 may be accessed through both the I2C and

SPI serial interfaces. The latter may be software configured to operate either in 3-wire or 4-

wire interface mode.

The serial interfaces are mapped onto the same pads. To select/exploit the I2C interface, the

CS line must be tied high (i.e. connected to Vdd_IO).

6.1

I2C serial interface

The LSM320HAY30 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 given in the table below.

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

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

to/from the interface. Both the lines are connected to Vdd_IO through a pull-up resistor

embedded inside the LSM320HAY30. When the bus is free, both the lines are high.

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

mode.

Table 7.

Serial interface pin description

Pin name

Pin description

SPI enable

I2C/SPI mode selection (1: I2C mode; 0: SPI enabled)

SCL

SPC

I2C serial clock (SCL)

SPI serial port clock (SPC)

SDA

SDI

SDO

I2C serial data (SDA)

SPI serial data input (SDI)

3-wire interface serial data output (SDO)

SA0

SDO

I2C less significant bit of the device address (SA0)

SPI serial data output (SDO)

Table 8.

Serial interface pin description

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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