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CHAPTER 16 MULTI-ADDRESS I
2
C
16.1 Overview of the Multi-address I
2
C
The Multi-address I
2
C is a simple bidirectional bus consisting of two wires that transfer
data among devices. These two Multi-address I
2
C bus interfaces allow internal
devices requiring address data to connect to one another with a minimum number of
circuits, making it possible to construct less expensive hardware using a fewer
number of PCBs.
The Multi-address I
2
C interface that supports Philips's Multi-address I
2
C bus
specification and Intel's SM bus specification provides master/slave transmission and
reception, arbitration lost detection, slave address/general call address detection,
generation and detection of start/stop conditions, and buss error detection.
I
Multi-address I
2
C Functions
The multi-address I
2
C interface is a simple structure bidirectional bus consisting of two wires: a
serial data line (SDA) and a serial clock line (SCL). Among the devices connected with these
two wires, information is transmitted to one another. By recognizing the unique address of each
device, it can operate as a transmitting or receiving device in accordance with the function of
each device. Among these devices, the master/slave relation is established.
The multi-address I
2
C interface can connect two or more devices to the bus provided the upper
limit of the bus capacitance does not exceed 400pF. It is a full-fledged multi-master bus
equipped with collision detection and communication adjustment procedures designed to avoid
the destruction of data if two or more masters attempt to start data transfer simultaneously.
This macro provides six addresses to implement the multi-address function.
A configuration example of the multi-address I
2
C interface is shown in Figure 16.1-1 "Multi-
address I
2
C block Diagram".
The communication adjustment procedure permits only one master to control the bus when two
or more masters attempt to control the bus so that messages are not lost or the contents of
messages are not changed. Multi-master means that multiple masters attempt to control the
bus simultaneously without losing messages.