Step2: The master device sends the address of the target slave device which is compared with all the slave devices’ addresses as connected to the SCL and SDL lines. Step1: First, the master device issues a start condition to inform all the slave devices so that they listen on the serial data line. The following steps are used to communicate the master device to the slave: The number of slave devices is connected to the master device with the help of the I2C bus, wherein each slave consists of a unique address to communicate it. The I2C bus protocol is most commonly used in master and slave communication wherein the master is called “microcontroller”, and the slave is called other devices such as ADC, EEPROM, DAC and similar devices in the embedded system. I2C Data Transfer Rates I2C Communication The 9-bit data is sent for each transfer wherein 8-bits are sent by the transmitter MSB to LSB, and the 9th bit is an acknowledgement bit sent by the receiver. The I2C protocol operates three modes such as: fast mode, high-speed mode and standard mode wherein the standard mode data speed ranges 0Hz to 100Hz, and the fast mode data can transfer with 0Hz to 400 KHz speed and the high speed mode with 10 KHz to 100KHz. It supports Multimaster communication, which means two masters are used to communicate the external devices. The I2C protocol used to connect a maximum of 128 devices that are all connected to communicate with the SCL and SDL lines of the master unit as well as the slave devices. Many slave devices are interfaced to the microcontroller with the help of the I2C bus through I2C level shifter IC for transferring the information between them. Hence, these lines or drain terminals are connected thorough pull-up resistors to VCC for conduction mode. The SDL and SCL pins of the master device are designed with the transistors in open state, so data transfer is possible only when these transistors are conducted. The open-drain is the concept for FET transistor wherein the drain terminal of the transistor is open state. Both these SCL and SDL lines are in open-drain state when there is no transfer between I2C peripherals. The SDL stands for the ‘serial data line’, and this signal is driven by either the master or the I2C peripherals. The SCL stands for a ‘serial clock line’ and this signal is always driven by the ‘master device’. The I2C is a serial bus protocol consisting of two signal lines such as SCL and SDL lines which are used to communicate with the devices.
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