I2C Protocol
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The document discusses the Inter-Integrated Circuit (I2C) protocol. It was developed by Philips in the 1980s as a simpler way to connect peripherals in devices like TVs that previously used separate wiring for each component. I2C uses just two bidirectional lines (SCL for clock and SDA for data) and allows for multiple master and slave devices to communicate at speeds up to 3.4 Mbps using 7- or 10-bit addressing. Devices operate on a master-slave model where the master controls the bus by generating the clock signal and addressing slave devices to send or receive data.
I2C Protocol
- 3. History • Before 1980’s in Tv Sets- Microcontroller connected to each peripheral by wire • Complex and Bulky Structure • Philips Developed Two wired Protocol-I2C • Reduced Complexity
- 4. Basic Characteristics • Two wired bus • Speed Normal mode-100kbps Fast mode-400kbps High Speed mode-3.4mbps • Data Transfer: Serial,8 bit oriented , bidirectional • Master slave approach with multimaster option • Addressing-7 bit or 10 bit unique addressing
- 5. Overview : • SCL : Serial Clock Line • SDA : Serial Data Line • Data transfer between devices connected to the bus • Master Slave Approach
- 6. Overview :Terms • • • • • • • Transmitter – The device sending data to the bus Receiver – Device receiving data from the bus Master – device initiating a transfer, generates to clock and terminates a transfer Slave – Device addressed by the master Multi-master – more than one master can attempt to control the bus Arbitration – procedure to insure that only one master has control of ther bus at any instant Synchronization – procedure to sync then clocks of two or more devices
- 7. Master and Slave • Master : - Controls the SCL - Starts and stops data transfer - Controls addressing of other devices • Slave : - Device address by master
- 8. Physical Structure: +5v Rp Rp Device 1 SCL SDA Device 2 Device 3
- 9. Special Start and Stop Conditions: • Only in Start and Stop conditions SDA is allowed to change while SCL is high • Data transfer mode : SDA is stable when SCL is High SDA SCL SDA SCL
- 10. Data Transfer • Every Byte put on SDA must be 8 bit long • Each Byte followed by Acknowledge bit • Transfer- MSB to LSB • When SCL is low- Data can be transfer
- 11. Advantages • Only two signal lines requires • Flexible data transmission rates • Each device on the bus is independently addressable • Devices have a simple Master/Slave relationship • Capable of handling multiple master communications by providing arbitration and communication collision detection
- 12. Disadvantages • Open Collector driver at master needs pull up resistance 2.2k on each line • High Power Requirement • Low Speed • Low Throughput
- 13. Comparison : I2C Vs SPI I2C SPI Requires only two lines Requires minimum four lines Low Speed Higher Speed Half Duplex Full Duplex Additional Signal select lines not required if devices increases Additional Signal select lines are required as devices increases More Power required Less Power Required Multimaster can be used easily Multimaster is difficult to implement