How do slave devices understand that the current piece of information is intended to one particular device and what exactly the device it is intended to? We will talk about it, but later. And now it is time to ask an important question: "What is unique about this type of device management?" It turns out that it’s possible to manage all subordinate slave subscribers only on two lines (not considering the third line - the common wire circuit). A slave subscriber must have two outputs, which are combined with similar outputs of other slave-devices, as well as with a master subscriber. Actually, the 12C bus has such appearance.
The concept of the bus is so simple that you can quickly develop a schematic circuit of a device, test it and, if necessary, build up the design with new elements or remove unnecessary ones. The method of software development can also be simplified, some standard subroutine libraries can be used. Practically all chips with the12C interface have characteristics that make them suitable for low voltage portable applications powered from galvanic cells. For example, they have high noise immunity, low power consumption, a wide range of supply voltage and the parameters of the weak dependence on the ambient temperature.
The interface of any device connected to the 12C bus is notable for its utmost simplicity. It consists of two open-drain transistors (collector) and two buffer elements with high input impedance. One of the outputs is called SDA (Serial Data Line). It is intended for connection to the serial data line. The second output has a short title of SCL (Serial Clock Line). It is used for connection to the clock line.