MPC8280 datasheet(1304/1386 Pages) FREESCALE

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2C Controller

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

40-2

Freescale Semiconductor

40.1

Features

The following is a list of the I2C controller’s main features:

•

Two-signal interface (SDA and SCL)

•

Support for master and slave I2C operation

•

Multiple-master environment support

•

Continuous transfer mode for automatic scanning of a peripheral

•

Supports a maximum clock rate of 2,080 KHz (with a CPM utilization of 25%), assuming a

100-MHz system clock.

•

Independent, programmable baud-rate generator

•

Supports 7-bit I2C addressing

•

Open-drain output signals allow multiple master configuration

•

Local loopback capability for testing

40.2

I2C Controller Clocking and Signal Functions

The I2C controller can be configured as a master or slave for the serial channel. As a master, the controller’s

BRG provides the transfer clock. The I2C BRG takes its input from the BRG clock (BRGCLK), which is

generated from the CPM clock; see Section 10.4, “System Clock Control Register (SCCR).”

SDA and SCL are bidirectional signals connected to a positive supply voltage through an external pull-up

resistor. When the bus is free, both signals are pulled high. The general I2C master/slave configuration is

shown in Figure 40-2.

Figure 40-2. I2C Master/Slave General Configuration

When the I2C controller is master, the SCL clock output, taken directly from the I2C BRG, shifts receive

data in and transmit data out through SDA. The transmitter arbitrates for the bus during transmission and

aborts if it loses arbitration. When the I2C controller is a slave, the SCL clock input shifts data in and out

through SDA. The SCL frequency can range from DC to BRGCLK/48.

40.3

I2C Controller Transfers

To initiate a transfer, the master I2C controller sends a message specifying a read or write request to an I2C

slave. The first byte of the message consists of a 7-bit slave port address and a R/W request bit. Note that

VDD

Master

Slave

(EEPROM, for example)

SCL

SDA

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