Serial protocols i2c

Each I2C slave device has a 7-bit address that needs to be unique on the bus. Some devices have fixed I2C address while others have few address lines which determine lower bits of the I2C address.

This makes it very easy to have all I2C devices on the bus with unique I2C address. There are also devices which have bit address as allowed by the specification. If bit 0 in the address byte is set to 1 then the master device will read from the slave I2C device. Master device needs no address since it generates the clock via SCL and addresses individual I2C slave devices.

The communication is initiated by the master device. It generates the Start condition S followed by the address of the slave device B1. If the bit 0 of the address byte was set to 0 the master device will write to the slave device B2. Otherwise, the next byte will be read from the slave device. It is a bus interface connection protocol incorporated into devices for serial communication. It was originally designed by Philips Semiconductor in Recently, it is a widely used protocol for short-distance communication.

Both these lines are pulled high. According to I2C protocols, the data line can not change when the clock line is high, it can change only when the clock line is low. The 2 lines are open drain, hence a pull-up resistor is required so that the lines are high since the devices on the I2C bus are active low. The data is transmitted in the form of packets which comprises 9 bits. Start and Stop Condition Repeated Start Condition : Between each start and stop condition pair, the bus is considered as busy and no master can take control of the bus.

If the master tries to initiate a new transfer and does not want to release the bus before starting the new transfer, it issues a new START condition. Skip to content. However, at the beginning of each message, the master sends a set of addressing bits. The result is that only one device will respond to the command, which will be the one to which the command is addressed. The other slave devices will ignore the command.

There are a considerable number of ICs available that can use an I 2 C bus. Some examples of these components and their applications are:. This article has looked at some features of the popular I 2 C protocol and discussed some of its advantages and implementation details.

In the other articles in this series , we will look at some of the alternate serial communication protocols available. Have more questions? Call an expert at Altium and discover how we can help you with your next PCB design. Mark Harris is an engineer's engineer, with over 12 years of diverse experience within the electronics industry, varying from aerospace and defense contracts to small product startups, hobbies and everything in between.

Before moving to the United Kingdom, Mark was employed by one of the largest research organizations in Canada; every day brought a different project or challenge involving electronics, mechanics, and software. He also publishes the most extensive open source database library of components for Altium Designer called the Celestial Database Library. Mark has an affinity for open-source hardware and software and the innovative problem-solving required for the day-to-day challenges such projects offer.

Electronics are passion; watching a product go from an idea to reality and start interacting with the world is a never-ending source of enjoyment. You can contact Mark directly at: mark originalcircuit. Mobile menu. Explore Products.

Altium Community. About Author Mark Harris is an engineer's engineer, with over 12 years of diverse experience within the electronics industry, varying from aerospace and defense contracts to small product startups, hobbies and everything in between. More content by Mark Harris. Recent Articles. Do you know when a power plane resonance occurs in the PDN on a circuit board? Read Article. What is Spreading Inductance? The spreading inductance of a plane pair has a simple meaning, but it can be difficult to calculate.