I2c

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Inter IC Communication:-

Inter IC Communication bus, often abbreviated as I2C bus, is a multi-master bi directional 2 wire serial bus for Inter IC communication, developed by Philips Semiconductor. The I2C bus consists of only two lines; one is called SDA (Serial Data line) carries the data bits and the other is called SCL (Serial Clock Line) is used as a clock signal. The messages sent over the I2C bus contain addresses to define which device should reply to them. All I2C-bus compatible devices incorporate an on-chip interface which allows them to communicate directly with each other via the I2C-bus. This design concept solves the many interfacing problems encountered when designing digital control circuits.

Before the introduction of I2C bus method, the method that was used for inter-IC communication was via a parallel 8 bit wide bus. This bus structure, which is also used to connect memory and peripherals to CPUs, requires apart from eight data lines for the data transfer, several lines for addressing specific peripheral ICs. When Philips introduced I2C this not only reduced the necessary area on the printed circuit boards but also the costs involved. This method reduced the number of communication lines to only two. Philips managed to reduce the number of data lines of the I2C bus by switching from parallel to synchronous serial communication.

Physical Design:-

I2C bus defines a data line SDA and a clock line SLC. These two lines create a synchronous serial bus. The number of devices that can be connected to the bus is only limited by the total allowed bus capacitance of 400 pF. Since most ICs with an I2C interface use low-power, high impedance CMOS technology, many ICs can be connected to the I2C bus before that maximum capacitance is reached. The clock signal on the bus is generated by one of the masters connected to the I2C bus. When idle, the SDA and SLC lines are pulled up to the supply voltage with a pull-up resistor.

I2C Bus Protocol:-

The I2C consist of two active wires i.e. SDA and SCL. Both of these wires support bi-directional communication. Every device, which is hooked to the bus, has its own unique address. Each of these chips can act as sender and/or receiver depending upon its functionality. The I2C bus is a multi-master bus. This means that more than one IC capable of initiating a data transfer can be connected to it. According to the I2C protocol specification, the IC that initiates a data transfer on the bus is considered the Bus Master.

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