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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors—I2C Bus Interface Unit
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
Developer’s Manual
August 2006
876
Order Number: 306262-004US
The I
2
C unit’s state machines and functionality are partially controlled by using local
memory mapped registers (MMRs) that store configuration and operation information.
The registers are controlled from the APB bus and reside in the i2c_registers block.
21.4
Theory of Operation
The I
2
C bus defines a serial protocol for passing information between agents on the I
2
C
bus using a two pin interface. The interface consists of an SDA line and an SCL. Each
device on the I
2
C bus is recognized by a unique 7-bit address and can operate as a
transmitter or as a receiver. In addition to transmitter and receiver, the I
2
C bus uses
the concept of master and slave.
lists the I
2
C device types.
Figure 190. I
2
C Bus Interface Unit Block Diagram
B4271-01
I
2
C Bus
Monitor
SCL
Generator
Address
Decode
Serial Shift Register
Internal Bus Interface
I
2
C Data Buffer Register (IDBR)
I
2
C Control Register (ICR)
I
2
C Status Register (ISR)
I
2
C Slave Address Register (ISAR)
I
2
C Clock Count Register (ICCR)
Count
Dat
a
Dat
a
In
te
rn
al B
u
s
Internal Bus Address and Control Signals
SCL
SDA
I2C_int_1
APB Bus
Table 276.
I
2
C Bus Definitions (Sheet 1 of 2)
I
2
C Device
Definition
Transmitter
Sends data to the I
2
C bus.
Receiver
Receives data from the I
2
C bus.
Master
Initiates a transfer, generates the clock signal, and terminates the transactions.