I²C Bus

[I²C Description]
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I²C Bus Description

I²C bus was developed by Philips Semiconductors [NXP], originally designed to be a battery control interface.
The I²C interface standard defines both the electrical layer and protocol layer.
The I²C bus uses a bi-directional Serial Clock Line [SCL] and Serial Data Lines [SDA]. Both the SCL and SDA lines are pulled high via an Rp resistor. Resistor Rs is optional, and used for ESD protection for 'Hot-Swap' devices. No other lines are specified. Any device may be a Transmitter or Receiver, and a Master or Slave. Data and clock are sent from the Master ~ valid while the clock line is high. The link may have multiple Masters and Slaves on the bus, but only one Master may be active at any one time. I2C Slaves may receive or transmit data to the master.

I2C Bus Speed

There are a number of speed grades available depending on the I2C specification version
Three speed modes are specified in the 2001 standard version:
Standard; 100kbps [Bits per Second], Fast mode; 400kbps, and High speed mode 3.4Mbps [HS Mode].
While the 2006 I2C version defines the Fast Mode Plus speed grade which increase the bus speed to 1MBps [1MHz].

I2C Communication

I2C, due to its two-wire nature (one clock, one data) can only communicate half-duplex. The maximum bus capacitance is 400pF, which sets the maximum number of devices on the I2C bus and the maximum line length. The interface uses 8 bit long bytes, MSB [Most Significant Bit] first, with each device having a unique address.

I2C Bus Voltage Levels

The voltage V_DD may be different for each device, but all devices have to relate their output levels to the voltage produced by the pull-up resistors [R_P] It is possible to run off two different bus voltages, but they have to be translated [refer to the spec.].

I²C Bus Terms

The I2C bus may also be seen as the Inter-IC Bus or the IIC Bus which all mean the same thing. The most common term is of course I2C.

{I2C Bus Index}

I2C Bus Interface IC Manufacturers

Analog Devices
{12-Bit Plus Sign Temperature Sensors with SMBus/I2C-Compatible Serial Interface}

Maxim
{10-Bit Temperature Sensors with I2C-Compatible Serial Interface, Digital Potentiometer}

NXP Semiconductors
{ICs with an I²C Bus}

Many ICs have the I2C interface including;
processors, controllers, GPIO Expanders, LCD Controllers, Temperature Sensors, and Bus Controllers.

IC Manufacturers {All types, or use the Components Icon below}

{I2C Bus Index}

I2C Bus Standards Information

The I2C Interface Specification may be down loaded from NXP [new name for Philips Semiconductor]
The I2C-Bus Specification, Version 2.1, January 2000; {Philips Semiconductor}
The above standard contains the Standard-Mode, Fast-Mode, and High Speed Mode [HS] upgrades.
The latest I2C revision; Fast Mode Plus [fm+] was released in April 2006
Previous Standards Revisions; I2C Version 1.0, 1992. I2C Version 2.0, 1998.
The I2C interface specification was developed by Philips Semiconductor

{Back to I2C Bus Index}

Access Bus Description

Access.Bus is a low speed serial bus that was aimed at the PC market.
Access.Bus uses the I²C bus as the electrical hardware interface.
A four pin modular type connector and a shielded 4 wire cable is called out in the specification.
ACCESS.bus operates at 100 Kbps with a maximum cable length is 10 meters.
Access.Bus uses the same signals as the I²C bus, and adds ground and power for the cable.
Refer to the main Access Bus page for more information on this interface bus, including pinouts and signal assignments.

Engineering Design Key words: I2C Bus, IIC Bus, Inter-IC Bus Standard, Interface Standard, Specification, Spec, AccessBus, Access.Bus, Access Bus, Interface, IC, Serial Bus, Battery Control Bus, Physical Interface, Description, Integrated Circuit, Interface, PC, Peripheral Interface, Chip-to-Chip.