Intel
®
81341 and 81342—I
2
C Bus Interface Units
Intel
®
81341 and 81342 I/O Processors
Developer’s Manual
December 2007
910
Order Number: 315037-002US
16.2
Theory of Operation
The I
2
C bus defines a serial protocol for passing information between agents on the I
2
C
bus, using only a two pin interface. The interface consists of a Serial Data/Address
(
SDA
) line and a Serial Clock Line (
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.
As an example of I
2
C bus operation, consider the case of the 81341 and 81342 acting
as a master on the bus (
). The 81341 and 81342, as a master, addresses an
EEPROM as a slave to receive data. The 81341 and 81342 is a master-transmitter and
the EEPROM is a slave-receiver. When the 81341 and 81342 reads data, the 81341 and
81342 is a master-receiver and the EEPROM is a slave-transmitter. In both cases, the
master generates the clock, initiates the transaction and terminates it.
Table 581. I
2
C Bus Definitions
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.
Slave
The device addressed by a master.
Multi-master
More than one master can attempt to control the bus at the same time without corrupting
the message.
Arbitration
Procedure to ensure that, when more than one master simultaneously tries to control the
bus, only one is allowed. This procedure ensures that messages are not corrupted.
Figure 140. I
2
C Bus Configuration Example
Microcontroller
Gate
Array
EEPROM
SCL
SDA
Intel® I/O
Processor
B6282-01