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How is the I2C bus arranged? Part 2

Version 2.0, released in 1998, introduced a high-speed bus specification mode (Hs-mode) with a transfer rate up to 3.4 Mbit/s. Moreover, the requirements demanded to introduce mandatory compatibility with low-speed and fast-speed modes. By the time version 2.0 appeared, the I2C bus had spread throughout the world, becoming an international standard. More than 1000 integrated circuits were developed, and the license for official use of the specification was purchased by more than 50 companies.

Version 2.1, dated 2000, includes insignificant modifications which are not reflected in version 2.0.

We will not go into all the details and intricacies of these versions. Let’s consider only the most necessary ones. If you want to learn more about the official documentation, you can easily get it from the Internet server of Philips (

It might be interesting that Philips singles out the chips equipped with 12C interface in its documentation.

Complete range of the chips with 12C interface manufactured by the company, currently has more than 150 items. They are made using a promising CMOS technology, as well as using bipolar technology, that has already become traditional.

Having defined the main provisions of the bus, let’s proceed to consider its hardware implementation. Let’s see it on the example of a modern car stereo unit.

A car stereo unit has a microcontroller acting as a master device that generates the required signal sequence and sends the information to slave devices and receives some information from them. Other devices connected to the bus will be subject to the microcontroller. According to certain rules called a protocol, the microcontroller can send to the display panel (slave device 1) data that shows, for example, the volume, the received radio frequency or timing of audio cassettes. If commanded by microcontroller, frequency synthesizer (slave device 2) resets the receiving frequency, volume and tone control (slave device 3), changes the volume and its "coloring".