The I2C-bus is a de facto world standard that is now implemented in over 1000 different ICs manufactured by more than 50 companies. Additionally， the versatile I2C-bus is used in various control architectures such as System Management Bus （SMBus）， Power Management Bus （PMBus）， Intelligent Platform Management Interface （IPMI）， Display Data Channel （DDC） and Advanced Telecom Computing Architecture （ATCA）。 This document assists device and system designers to understand how the I2C-bus works and implement a working application. Various operating modes are described. It contains a comprehensive introduction to the I2C-bus data transfer， handshaking and bus arbitration schemes. Detailed sections cover the timing and electrical specifications for the I 2C-bus in each of its operating modes. Designers of I2C-compatible chips should use this document as a reference and ensure that new devices meet all limits specified in this document. Designers of systems that include I2C devices should review this document and also refer to individual component data sheets.