L3GD20 datasheet(22/44 Pages) STMICROELECTRONICS

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Digital interfaces

L3GD20

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Doc ID 022116 Rev 1

Digital interfaces

The registers embedded in the L3GD20 may be accessed through both the I2C and SPI

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

interface mode.

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

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

5.1

I2C serial interface

The L3GD20 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 lines must be connected to Vdd_IO through external pull-up

resistors. When the bus is free, both lines are high.

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

mode.

Table 9.

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 port clock (SPC)

SDA/SDI/SDO

I2C serial data (SDA)

SPI serial data input (SDI)

3-wire interface serial data output (SDO)

SDO

SPI serial data output (SDO)

I2C less significant bit of the device address

Table 10.

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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