I2C Bus Interface Unit

9

This chapter describes the Inter-Integrated Circuit (I2C) bus interface unit, including the operation modes and setup for the PXA255 processor.

9.1Overview

The I2C bus was created by the Phillips Corporation and is a serial bus with a two-pin interface. The SDA data pin is used for input and output functions and the SCL clock pin is used to control and reference the I2C bus. The I2C unit allows the processor to serve as a master and slave device that resides on the I2C bus.

The I2C unit enables the processor to communicate with I2C peripherals and microcontrollers for system management functions. The I2C bus requires a minimum amount of hardware to relay status and reliability information concerning the processor subsystem to an external device.

The I2C unit is a peripheral device that resides on the processor internal bus. Data is transmitted to and received from the I2C bus via a buffered interface. Control and status information is relayed through a set of memory-mapped registers. Refer to The I2C-Bus Specification for complete details on I2C bus operation.

Note: The I2C unit does not support the hardware general call, 10-bit addressing, or CBUS compatibility.

9.2Signal Description

The I2C unit signals are SDA and SCL. Table 9-1describes each signal’s function.

Table 9-1. I2C Signal Description

Signal Name

Input/Output

Description

 

 

 

SDA

Bidirectional

I2C Serial Data/Address signal

SCL

Bidirectional

I2C Serial Clock Line signal

9.3Functional Description

The I2C bus defines a serial protocol for passing information between agents on the I2C bus using a two pin interface that consists of a Serial Data/Address (SDA) line and a Serial Clock Line (SCL). Each device on the I2C bus is recognized by a unique 7-bit address and can operate as a transmitter or as a receiver in master or slave mode. Table 9-2lists the I2C operation modes.

Intel® PXA255 Processor Developer’s Manual

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Intel PXA255 manual I2C Signal Description, Signal Name Input/Output Description, Sda, Scl