14-09-2013, 03:57 PM
I2C Bus Technical Overview
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ABSTRACT
The I2C (Inter-Integrated Circuit) Bus is a two-wire, low to medium speed,
communication bus (a path for electronic signals) developed by Philips
Semiconductors in the early 1980s. I2C was created to reduce the manufacturing
costs of electronic products. It provides a low-cost, but powerful, chip-to-chip
communication link within these products. Initial applications for I2C included
volume and contrast control in radios and televisions. Over the past decade, I2C
has expanded its communications role to include a wide range of applications.
Industry Standard
The “I2C Bus Specification,” published by Philips Semiconductor, provides a communication
protocol definition of the signal activity on the I2C Bus. This specification helps instruct
semiconductor device manufacturers, and electronic product developers, in the correct use of the
technology. The specification is freely available on the Internet
(www.semiconductors.philipsbuses/i2c/).
Low Cost
Prior to I2C, chip-to-chip communications used many wires in a parallel
interface, often requiring ICs (integrated circuits) to have 24, 28, or more
pins. Many of these pins were used for inter-chip addressing, selection,
control, and data transfers. In a parallel interface, 8 data bits are typically
transferred from a sender IC to a receiver IC in a single operation.
Multiple Devices
I2C can connect many ICs on just two-wires. Each I2C slave device has its own unique slave
address. When a master sends a message, it includes the slave address at the beginning of the
message. All devices on the bus hear the message, but only the slave that recognizes its own
address participates in the transfer.
Multi-Master Support
I2C also supports multiple master devices on the bus at the same time, a powerful feature that
optimizes bus use by keeping bus message traffic to a minimum. To support multiple masters,
I2C must resolve signal conflicts, should two or more master devices try to talk on the bus at the
same time. This feat, called bus arbitration loss detection, allows a master to detect when its bus
signals are conflicting with those of another master. A master that detects arbitration loss
terminates its use of the bus, allowing the message generated by another master to cross the bus
unharmed.
Summary
The I2C Bus is a time-proven, industry standard, communication protocol used in a wide variety
of electronic products. Its low cost and powerful features make I2C ideal for low to medium
speed chip-to-chip communications.
I2C is supported by a large and growing number of semiconductor and system manufacturers.
These companies offer a variety of electronic devices, including memories, input and output
devices, sensors of many types, real-time clocks, displays, data entry devices, and much more.
I2C is an effective technology that can lower product costs and increase product performance.
For more information about the I2C Bus, applications, tools, and components, visit MCC’s
website at www.mcc-us.com.