In order to avoid confusion, the bus signal required when the output of the device is connected to the bus must be drain open circuit (OD) and output (OC) or open collector output, serial data line SDA on the equipment should be a two-way interface circuit, output circuit is used to send data to the bus, the input circuit for receiving the data on the bus, and a serial clock line should also be a two-way street, as the host of the control bus data transfer, on the one hand, to send the clock signal by SCL output circuit, on the other hand to inspect the SCL level on the bus, in order to decide when to send a clock pulse level; For acceptance of the host command from the machine, to press the SCL signal on the bus or receiving the signal on the SDA, can also sent the SCL line is low level signal to extend the bus clock signal cycle, when the bus is idle, for each device is open drain output, pull-up resistor Rp keep SDA and SCL line is high level, any equipment output low level will make the corresponding bus signal is low, that is to say, each device SDA is "and" relationship, SCL is also "and" relationship,
Bus interface circuit of equipment manufacturing technology and level are no special requirements (NMOS and CMOS can compatible), on the I2C bus data transfer rate can be as high as one hundred thousand bits per second, high-speed way above four hundred thousand bits per second, on the other hand, the bus allows the connection device of the electric capacity of not more than 400 pf in the limit,
Bus run (data) is controlled by the host, the host refers to the start of data transmission (signal to start), made the clock signal, and at the end of the transmission signal to stop the equipment, the host usually is a microprocessor, the host after the device is called from the machine, in order to communicate, each received the I2C bus equipment has a unique address, so that the host search, data transmission between host and from the machine and can by the host to send data from the machine, also can from the machine to the host, who sends data to the bus device called a transmitter, receiving data from the bus equipment, known as receptors,
I2C bus is allowed to connect multiple microprocessor and various peripheral devices, such as memory, LED and LCD driver, A/D and D/A converter, etc., in order to ensure that the data transmitted reliably, bus at any time can only be controlled by A host, the microprocessor should start in bus free time send data, in order to properly solve many sets of microprocessors and start sending data transmission control (bus) conflict, and decide which one is the microprocessor control bus, I2C bus to allow connect different transmission rate of the equipment, the clock signal synchronization process between multiple devices called synchronization
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