I2C bus communication protocol

I2C bus communication protocols 

What is 12c:

-Inter Integrated Circuit

-Bidirectional Data Transfer

-Half duplex (have only one data line)

-Synchronous bus so data is clocked with clock signal

-Colock is controlled when data line is changed.

Speed of 12c:

low (under 100 kbps)

Fast (400 kbps)

high speed (3.4 mbps) 12C V2.0

2 wire communication:

SDA and SCL

Vtg high = 1, low = 0.

when SLC =1, it is valid data, when SLC=0, data is changed .

Basic protocol is master slave protocol

-Master controls the clock

-Slave device may hold the clock low to prevent data transfer

-no data transfer is present when clock is low

-It is a kind of wired and connection

-need to put pullup resistor

-default it is a open-drain or open-collector, so that adding pull up resistor is necessary so that it

will have only two states that is 1.floating high and 2.drive low

-Default state is high when no device is pulling it low.

Data Transfer:

• It is byte oriented (bit)
• Ack transmited by recepient of the data
• MSB first
• First byte is address
• First byte is transmitted by master and addressed slave is the recepient
• Next byte is based on the last bit (R/ W)
• 7 bit address
• 1 bit R/ W
• 0-master write 
• First byte is transmitted by master and addressed slave is the recepient
• Next byte is based on the last bit (R/ W)
• 7bit address
• 1 bit R/ W
• 0-master write

1-master receiver.

 

Full I2C transfer:

12C Multi Master:

• It is a multi master bus
• So bus arbitration is required
• 1
• When two device tries to drive SDA to different value
• It is necessary to be sure that is not interfiering with another message
• If a device is trying to send logic one but hears logic 0, it immediately stops transmission and gives
• the other sender priority
• Synch needed in SCL

Advantages:

• Good for comm in On-board devices
• mc
• Easy to link multiple devices because of addressing scheme
• Cost and complexity do not scale up with the num of devices

Disadvantages:

The complexity of supporting software components can be higher than that of scheme (EX. SPI-No

need of address in SPI)