I²C (Inter-Integrated Circuit), pronounced I-squared-C, is a synchronous, multi- master, multi-slave, packet switched, single-ended, serial computer bus invented in by Philips Semiconductor (now NXP Semiconductors). Alternatively I²C is spelled I2C (pronounced I-two-C) or IIC (pronounced I-I-C). Since October Industry Standard. The “I2C Bus Specification,” published by Philips Semiconductor, provides a communication protocol definition of the signal activity on the I2C. I2C specification defines the interface, signals, addressing, protocols and electrical The I2C bus uses two wires: serial data (SDA) and serial clock (SCL). . A complete I2C Bus Specification and User Manual can be obtained from the NXP.

Author: Voodoolmaran Gogar
Country: Russian Federation
Language: English (Spanish)
Genre: Politics
Published (Last): 6 September 2008
Pages: 164
PDF File Size: 11.17 Mb
ePub File Size: 3.2 Mb
ISBN: 344-1-67808-414-1
Downloads: 53547
Price: Free* [*Free Regsitration Required]
Uploader: Vudot

The number of the devices on a single bus is almost unlimited philips i2c protocol the only requirement is that the bus capacitance does not exceed pF. The communication starts with the Start condition, followed by the 7-bit slave address and the data direction bit. If the master only writes to the slave device then the data transfer direction is not changed.

All devices on the bus must have open-collector or open-drain pins. After the slave address and the data direction is sent, the master can continue with philiips or writing.

Profocol example is written in pseudo C. After the Philips i2c protocol condition the bus is considered as busy and can be used by another master only after a Stop condition is detected. Archived philips i2c protocol the original PDF on This method requires that all other devices on the bus have thresholds which are compatible and often means that multiple buffers implementing this scheme cannot be put in series with one another. However, most modern I2C controllers support all speeds and addressing modes.

Logic analyzers are tools that collect, analyze, decode, and store signals, so people can view the high-speed i2cc at their leisure. One master may lose arbitration to an incoming message, and must change its role from master to slave in time to acknowledge its own address. Two or three pins is typical, and with many devices, there are three or more wiring options per address pin. Slave devices that need some time to process received byte or are not ready yet to send the next byte, can pull the clock low to signal to the master that it should philips i2c protocol.


SMBus is restricted to nine of those protocok, philips i2c protocol as read word N and write word Ninvolving a single slave. Potocol this situation, the master is philips i2c protocol master receive mode, and the slave is in slave transmit mode.

Such start byte is followed by an acknowledge pulse for interface compatibility reasons. If the transmitter sees a “1” bit NACK instead, it learns that:. The system must be designed in such a way that slower devices can protcol with the philips i2c protocol without slowing down faster ones. TV signal processing, audio processing, SMBus.

For example, a buffer may have an input threshold of 0. It can do so without problems because so far the philips i2c protocol has been exactly as it expected; no other transmitter has disturbed its message.

Arbitration occurs very rarely, but is necessary for proper multi-master support.

I²C – Wikipedia

Each message begins with a start symbol, philips i2c protocol the transaction ends with a u2c symbol. Since the two masters may send messages philips i2c protocol the same slave address, and addresses sometimes refer to multiple slaves, arbitration must continue into the data stages. Additionally, master and slave roles may be changed between messages after a Hpilips is sent.

Views Read Edit View history. If the master needs to communicate with other slaves it can generate a repeated start with another slave address without generation Stop condition.

Specification – I2C Bus

There can by any combination of the devices philips i2c protocol the bus regardless of the supported speed and addressing. Activating the line means pulling it down wired ;hilips. An addressed slave device may hold the clock line SCL low after philips i2c protocol or sending a byte, indicating that it is not yet ready to process more data. Arbitration For normal data transfer on the I2C bus only one master can be active. However, with the advance of the technology, needs for higher transfer rates and larger address space emerged.

The communication is ended with the Stop condition which also signals that philips i2c protocol I2C bus is free. If this bit is 0 then the master will write to the slave device. Thus the actual transfer rate of user data is lower than protkcol peak bit rates alone would imply.


Access Denied

Synchronization Each master must generate its own clock signal and the data can change only when the clock is low. In some cases it is very hard to avoid philips i2c protocol collisions since 7 bits for I2C addresses allow only different addresses where only can actually be used.

Start Byte If microcontroller has I2C hardware and the microcontroller acts as a slave then the software needs to do nothing to check the bus state. High-speed mode introduces also few differences or improvements in the specifications:.

System Philips i2c protocol Interface Forum.

Data on the I2C bus is transferred in j2c packets bytes. Home I2C Bus Specification. When used on SCL, this is called clock stretching and used as a flow-control mechanism for slaves. An important consequence of this is that multiple nodes may be driving the lines simultaneously.

Communication With 7-bit I2C Addresses Each slave device on the bus should have a unique 7-bit address. Many complex embedded philips i2c protocol contain a philips i2c protocol number of different I2C devices. All devices must at least partially support the highest speed philips i2c protocol or they may spuriously detect their device address. The general call address is used to address all devices on the slave bus. Automatic bus configuration is a related issue.

Many other bus technologies used in similar applications, such as Serial Peripheral Interface Bus SPIrequire more pins and signals to connect multiple devices.


There philips i2c protocol cases where large amount of data needs to be transferred. This bit signals whether the device is ready to proceed with the next byte. If the slave is clock-stretching, the clock line will still be low because the connections are open-drain. Philips i2c protocol mode introduces also few differences or philipx in the specifications: Because logical 1 level depends on the supply voltage, there is no standard bus voltage.

Two groups of 8 I2C addresses are reserved for future uses and one address is used for bit I2C addressing.