Motorola MPC8260 User Manual

MOTOROLA

Chapter  34.  I2C Controller  

34-1

340

340

The inter-integrated circuit (I

2

C¨) controller lets the MPC8260 exchange data with other

I

2

C devices, such as microcontrollers, EEPROMs, real-time clock devices, A/D converters,

and LCD displays. The I

2

C controller uses a synchronous, multimaster bus that can connect

several integrated circuits on a board. It uses two signalsÑserial data (SDA) and serial
clock (SCL)Ñto carry information between the integrated circuits connected to it.

As shown in Figure 34-1, the I

2

C controller consists of transmit and receive sections, an

independent baud-rate generator (BRG), and a control unit. The transmit and receive
sections use the same clock, which is derived from the I

2

C BRG when in master mode and

generated externally when in slave mode. Wait states are inserted during a data transfer if
SCL is held low by a slave device. In the middle of a data transfer, the master I

2

C controller

recognizes the need for wait states by monitoring SCL. However, the I

2

C controller has no

automatic time-out mechanism if the slave device does not release SCL; therefore, software
should monitor how long SCL stays low to generate bus timeouts.

Control

Tx Data Register

Rx Data Register

Peripheral Bus

Mode Register

Shift Register

Shift Register

Baud-Rate Generator

SCL

SDA

60x Bus