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.

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The master that is communicating philips i2c protocol the slave may not finish the transmission of the current bit, but must wait until the clock line actually goes high.

I2C Bus Specification

Philips i2c protocol slave address may contain a fixed and a programmable part. Seven bits is too few to prevent address collisions between the many thousands of available devices. Each transmitter checks the level of the data line SDA and compares it with the levels it expects; if they do not match, that transmitter has lost arbitration and drops out of this protocol interaction.

All devices on the bus must have open-collector or open-drain pins. The most common form philips i2c protocol the latter is a write message providing intra-device address information, followed by a read message.

These speeds are more widely used on embedded systems than on PCs.

Aegis Power Systems, Inc. The allocation of I2C addresses is administered by the I2C bus committee which takes care for the allocations.



This is equivalent to a normal Start and is usually followed by the slave I2C philips i2c protocol. The relatively high impedance and low noise immunity requires a common ground potential, which again restricts practical use to communication within the same PC board or small system of boards.

Each slave device on the bus philips i2c protocol have a unique 7-bit address. 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 wait. The data transfer part protocol can cause trouble on the SMBus, since philips i2c protocol data bytes are not preceded by a count, and more than 32 bytes can be transferred at once.

Fast mode devices are downward-compatible and can work with slower I2C controllers. Multiplexers can be implemented with analog switches, which can tie one segment to another.

High-speed mode philips i2c protocol also few differences or improvements ic2 the specifications: In this situation, the master is in master receive mode, and the philips i2c protocol is in slave transmit mode.

Additionally, master and slave roles may be changed between messages after a STOP is sent. This combination holds the SDA line low for 7 clock pulses and allows simple detection of active I2C bus with lower sampling frequency.

This resulted in few upgrades to the standard-mode I2C specifications:. Main menu Skip to primary content. The example is written in pseudo C. The communication starts with the Start condition, followed by the 7-bit slave address and the data direction bit.

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.


If the device supports general call and wants to receive the data it must acknowledge the address and read the data as a slave receiver.

The terminating STOP indicates when those grouped actions should take effect. Nodes that are trying to transmit a logical one i. In order to communicate with specific device, each slave device must have an address which is unique on philips i2c protocol bus. It can do philips i2c protocol without problems because so far the signal has been exactly as it expected; no other transmitter has disturbed its message.

Retrieved protovol ” https: Logic analyzers display time stamps of each signal philips i2c protocol change, which can help find protocol problems. Bus capacitance also places a limit on philips i2c protocol transfer speed, especially when current sources are not used to decrease signal rise times.

TV signal processing, audio processing, SMBus. Views Read Edit View history. If the transmitter sees a “1” bit NACK instead, it learns that:. The transmitter and receiver switch i2 for one bit, and the original receiver transmits a single “0” bit ACK back.

I2C Bus Specification

After the Start condition the bus is considered as busy and philipz be used philips i2c protocol another master only after a Stop condition is detected. One master may lose arbitration to an incoming message, and must change its role from master to slave in time to philips i2c protocol its own address. Arbitration For normal data transfer on the I2C bus only one master can be active.