Motorola MPC8260 - Manual (Page 943)

MOTOROLA Chapter 34. I2C Controller 34-1
Chapter 34
I
2
C Controller
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.
Figure 34-1. I 2 C Controller Block Diagram
Control
Tx Data Register Rx Data Register
Peripheral Bus
Mode Register
Shift Register Shift Register
Baud-Rate Generator SCL
SDA
60x Bus