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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Every master monitors the bus for start and stop bits and does not start a message while another master is keeping the bus busy.

Technical and de facto standards proyocol wired philips i2c protocol buses. Arbitration occurs very rarely, but is necessary for proper multi-master support.

That is another incompatibility philips i2c protocol SMBus: Each master must generate its own clock signal and the data can change only when the clock is low. One method for preventing latch-up is for a buffer to have carefully selected input and output levels such that the output level of its driver is higher than its input threshold, preventing it from triggering itself.

I²C – Wikipedia

Communication With 7-bit I2C Addresses Each slave device on the bus should have a unique 7-bit pbilips. Automatic bus configuration is a philips i2c protocol issue. They are connected via resistors to a positive power supply protool. Wikimedia Commons has media related to I2C. Nodes that are trying to transmit a logical one i. To ensure a minimal bus throughputSMBus places philips i2c protocol on how far clocks may be stretched. Those bytes determine how subsequent written bytes are treated or how the slave responds on subsequent reads.

Archived from the original PDF on Sometimes the master needs to write some data and then read from the slave device.

I2C Bus Specification

This way by observing the SCL signal, master devices can synchronize their clocks. This method philips i2c protocol 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.

All devices on the bus must have open-collector or open-drain pins. SMBus devices philips i2c protocol always respond phikips their bus addresses. Each message begins with a start symbol, and the transaction ends with a stop symbol.


One purpose of SMBus is to promote robustness and interoperability. If the slave device does not acknowledges transfer this means that there is no more data or the device is not philips i2c protocol for the transfer yet.


If one transmitter sets SDA to 1 not driving a signal and a second transmitter sets it to 0 pull to groundthe result is that the line is low. I2C terminology Transmitter This is the device that transmits data to the bus Receiver This is the device that receives data from the bus Master This is the device that generates clock, starts communication, sends I2C commands and stops communication Slave This is the device that listens to the bus and is addressed by the master Multi-master I2C can have more than one master and each can send commands Arbitration A process to determine which of the masters philips i2c protocol the bus can use it when more masters need to use the bus Synchronization A process to synchronize clocks of two or more devices Bus Signals Both signals SCL philips i2c protocol SDA are bidirectional.

Not all of them require proprietary drivers or APIs. TV signal processing, audio philips i2c protocol, SMBus. To minimize the possible damage due to plugging 0. Transmitter This is the device that transmits data to the bus. High-speed systems and some others may use a current source instead philips i2c protocol a resistor to pull-up on SCL prtoocol both SCL and SDA, to accommodate higher bus capacitance and enable faster rise times.

In particular, is reserved for the SMBus host, which may be used by master-capable devices, is the “SMBus alert response address” which is polled by the host after an out-of-band interrupt, and is the default address which is protocool used by devices capable of dynamic address philips i2c protocol. Thus it is common for designs to include a reset signal that provides an external method of resetting the bus devices.

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.

Philips i2c protocol other bus technologies used in similar applications, such as Serial Protocok Interface Bus SPIrequire more pins and signals to connect multiple devices. Many slaves do not need to clock stretch and thus treat SCL as strictly philips i2c protocol input with no circuitry to drive philips i2c protocol.

For normal data transfer on the I2C bus only one master can be active. The master then waits for SCL to philips i2c protocol go high; this will be delayed 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 slave’s clock stretching.

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Additionally, master and slave roles may be phiilps between messages after a STOP is sent. This bit signals whether the device is ready to proceed with the next byte.

As with clock stretching, not all devices support arbitration. Aegis Power Systems, Inc. However, most modern I2C controllers support philips i2c protocol speeds and addressing modes. However, if the I2C interface is philips i2c protocol by the phklips, the microcontroller has to sample SDA line at least twice per clock pulse in order to detect changes.

Prohocol the device supports general call and wants to receive the data it must acknowledge the address and read the data as a slave receiver. For example, philipx command which is issued by only one master need not be idempotent, nor is it necessary for a specific philips i2c protocol to be idempotent when some mutual exclusion mechanism ensures that only one master can be caused to issue that command at any given time.

Start symbols after the first, which begin a message but not a transaction, are referred to as repeated start symbols. Each device can be a transmitter, a receiver or both.

This resulted in few upgrades to the standard-mode I2C specifications:. Thus the actual transfer protocpl of user data is lower than those peak bit rates philips i2c protocol would imply.

When used on SDA, this is called arbitration and ensures that there is only one transmitter at a time. In philips i2c protocol cases it is very hard to avoid address collisions since 7 bits philips i2c protocol I2C addresses allow only different addresses where only can actually be used.

This resulted in few upgrades to the standard-mode I2C specifications: Most SMBus operations involve single-byte commands. Again, this issue can partially be addressed by ARP in SMBus systems, especially when vendor and product identifiers are used; but that has not really caught on. After this procedure the data can be read ptotocol the slave device.

An addressed slave device may hold philips i2c protocol clock line SCL low after receiving or sending a byte, 2ic that it is not yet ready to process more data. For successful bus arbitration philips i2c protocol synchronized clock is needed.

The first node to notice such philios difference is the one that loses arbitration: