A3G4250D Просмотр технического описания (PDF) - STMicroelectronics

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A3G4250D

MEMS motion sensor: 3-axis digital output gyroscope

STMicroelectronics 

A3G4250D

5

Digital interfaces

Digital interfaces

The registers embedded in the A3G4250D 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 pins. To select/exploit the I2C interface, the

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

Table 11. Serial interface pin description

Pin name

Pin description

CS

SCL/SPC

SDA/SDI/SDO

SPI enable

I2C/SPI mode selection (1: SPI idle mode / I2C communication enabled; 0: SPI

communication mode / I2C disabled)

I2C serial clock (SCL)

SPI serial port clock (SPC)

I2C serial data (SDA)

SPI serial data input (SDI)

3-wire interface serial data output (SDO)

SDO

SPI serial data output (SDO)

I2C least significant bit of the device address

5.1

I2C serial interface

The A3G4250D I2C is a bus slave. The I2C is employed to write data to registers whose

content can also be read back.

The relevant I2C terminology is given in the table below.

Table 12. I2C terminology

Term

Description

Transmitter

Receiver

The device which sends data to the bus

The device which receives data from the bus

Master

Slave

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

transfer

The device addressed by the master

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_IO through an external pull-up

resistor. 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.

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