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: Gogis Maugor
Country: Republic of Macedonia
Language: English (Spanish)
Genre: Travel
Published (Last): 22 March 2004
Pages: 277
PDF File Size: 2.59 Mb
ePub File Size: 5.27 Mb
ISBN: 499-8-18619-221-4
Downloads: 70761
Price: Free* [*Free Regsitration Required]
Uploader: Shagrel

After this the data transfer direction is changed and the master device starts reading the data. 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.

The bus has two roles for nodes: Many other bus technologies used in similar applications, such as Serial Peripheral Interface Bus SPIrequire more pins and signals to philips i2c protocol multiple devices.

For this reason, when a slave can be accessed by multiple masters, every command recognized by the slave either must be idempotent philips i2c protocol must be guaranteed never to be issued by two masters at the same time.

This combination holds the SDA line low for 7 clock pulses and allows simple detection of active I2C bus philips i2c protocol lower sampling frequency. Some devices philips i2c protocol masters — they generate bus clock and initiate communication on the bus, other devices are slaves and respond to the commands on the bus.

This page was last edited on 16 Julyat High-speed mode introduces also few differences or improvements in the specifications: The general call address is used to address all devices on the slave bus. Except for the start and stop signals, the SDA line only changes while the clock is low; transmitting a data bit consists of pulsing the clock line high while holding the data line steady at the desired level. If there is more than one master, all but one of them will normally lose arbitration.

Skip to secondary philips i2c protocol.

I²C – Wikipedia

All I2C master and slave devices are connected with only those two wires. Message semantics are otherwise product-specific.

Such Prltocol interface is used by many hundred Philips i2c protocol devices from many manufacturers since its philips i2c protocol in the 80s. The number of the devices on a single bus is almost unlimited — the only requirement is that the bus capacitance does not exceed pF.

That is another incompatibility with SMBus: A transaction consisting of a single message is called either a read or a write transaction.

The complexity and the cost of connecting all those devices together must be kept to a minimum.

Synchronization Each master must generate its own clock signal and the data can change only when the clock is low. Automatic bus configuration is a related issue. AV processors and decoders, audio power amplifiers, Philips i2c protocol. Bus capacitance also places a limit on the transfer speed, especially when current sources are not used to decrease signal rise times.

There may be four potential modes of operation philips i2c protocol a given bus device, although most devices only use a single role and its two modes:.

For example, a command which is issued by only one master need not be idempotent, nor is it necessary for a specific command to be idempotent when some mutual exclusion mechanism ensures that only one master can be caused to issue that command at any given time.

However, two masters may start transmission at about the same time; in this case, arbitration occurs. Sometimes the master needs to write some data and then read from the slave device. Most logic analyzers have the capability to decode bus signals into high-level protocol data protocil show ASCII data.

The philipps philips i2c protocol to notice such a difference is the one that loses arbitration: The terminating Philips i2c protocol indicates when those grouped actions should take effect.

Access Denied

Seven bits is too few to prevent address collisions between the many thousands of available devices. A slave address may contain a fixed and a programmable part. Transmitter This is the protcol that philils data to the bus.

The master then waits for SCL philips i2c protocol actually go high; this will be philis by the finite rise time of the SCL signal the RC time constant of the pull-up resistor and the parasitic capacitance of the bus and may be additionally delayed by a philips i2c protocol clock stretching. However, if the I2C interface is implemented by the software, the microcontroller has to sample SDA line at least twice per clock pulse in order to detect changes.

The master is initially in master transmit mode by sending a START followed philips i2c protocol the 7-bit philips i2c protocol of the slave it wishes to communicate with, which is finally followed by a single bit representing whether it wishes to write 0 to or read 1 from the slave.

Philips i2c protocol Commons has media related to I2C. Receiver This is the device that receives data from the bus. There can i2d any combination of the devices on the bus regardless of the supported speed and addressing. However, with the advance of the technology, needs for higher transfer rates and larger address space emerged. Some slave devices have philips i2c protocol bits of the I2C address dependent on the level of address pins.

A given address may be used by a number of different protocol-incompatible devices in various systems, and hardly any device types can be detected at runtime.


The master device must either generate Stop or Repeated Start condition. One master may lose arbitration to an incoming philipd, and must change its role from master to slave in time to acknowledge its own address. Philips i2c protocol data transfer philips i2c protocol protocol can cause proyocol on the SMBus, since the data bytes are not preceded by a count, and more than 32 bytes can be transferred at once.

The bus is a multi-master buswhich means that any number of master nodes can be present.