I2C Controller
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
39-2 Freescale Semiconductor
39.1 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
39.2 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. 8, “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 39-2.
Figure 39-2. 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.
39.3 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
VDD
Master Slave
(EEPROM, for example)
SCL SCL
SDASDA