I3G4250D Datasheet, PDF (21/43 Pages) STMicroelectronics – 3-axis digital output gyroscope

I3G4250D
5
Digital interfaces
Digital interfaces
The registers embedded in the I3G4250D 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 to the same pins. To select/exploit the I²C interface, the
CS line must be tied high (i.e., connected to Vdd_IO).
Pin name
CS
SCL/SPC
SDA/SDI/SDO
SDO
Table 11. Serial interface pin description
Pin description
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)
SPI serial data output (SDO)
I²C least significant bit of the device address
5.1
I²C serial interface
The I3G4250D 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.
Term
Table 12. I²C terminology
Description
Transmitter
Receiver
Master
Slave
The device which sends data to the bus
The device which receives data from the bus
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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