Intel® PXA26x Processor Family Developer’s Manual 9-3
Inter-Integrated Circuit Bus Interfac e Un i t
9.3.1 Operational Blocks
The I2C unit is connected to the peripheral bus. The processor interrupt mecha nis m can be used to
notify the CPU that there is activity on the I2C bus. Polling can be used instead of interrupts. The
I2C unit consists of the two wire interface to the I2C bus, an 8-bit buffer for passing data t o and
from the processor, a set of control and status registers, and a shift register for parallel/serial
conversions.
The I2C unit initiates an interrupt to the processor when a buffer is full, a buffer is empty, the I2C
unit slave address is detected, arbitration is lost, or a bus error condition occurs. All interrupt
conditions must be cleared explicitly by software. See Section9.9.4, “I2C Status Re gister” for
details.
The 8-bit I2C Data Buffer Register (IDBR) is loaded with a byte of data from the shift register
interface to the I2C bus when receiving data and from the process or int ern al bus w hen wr itin g data.
The serial shift register is not user accessible.
The I2C Control Register (ICR) and the I2C Status Register (ISR) are located in the I2C memory-
mapped address space. The registers and their functions are defined in Section 9.9, “Register
Definitions”.
The I2C unit supports a fast mode opera tion of 400 Kbits/sec and a st andard mode of 100 Kbits/se c.
Refer to the I2C-Bus Specification for details.
9.3.2 Inter-Integrated Circuit Bus Interface Modes
The I2C unit can accomplish a transfer in different operation modes. Table 9-3 summarizes the
different modes.
Table 9-3. Modes of Operation
Mode Description
Master – Transmit
I2C unit acts as a master.
Used for a write operation.
I2C unit sends the data.
I2C unit is responsible for clocking.
Slave device in slave-receive mode
Master – Receive
I2C unit acts as a master.
Used for a read operation.
I2C unit receives the data.
I2C unit is responsible for clocking.
Slave device in slave-transmit mode
Slave – Transmit
I2C unit acts as a slave.
Used for a master read operation.
I2C unit sends the data.
Master device in master-receive mode.
Slave – Receive (default)
I2C unit acts as a slave.
Used for a master write operation.
I2C unit receives the data.
Master device in master-transmit mode.