Operation Modes

• Master Transmitter
• Master Receiver
• Slave Transmitter
• Slave Receiver

The Protocol

• Transactions are initiated and completed by the master.
• All messages have an address frame and a data frame.
• Data is placed on the SDA line after SCL goes low, and it is sampled after the SCL line goes high.

Start and Stop condition

• All transactions begin with START and are terminated by STOP
• A HIGH to LOW transition on the SDA line while SCL is HIGH defines a START condition
• A LOW to HIGH transition on the SDA line while SCL is HIGH defines a STOP condition.
• START and STOP conditions are always generated by the master
• The bus is considered to be free again a certain time after the STOP condition
• The bus stays busy if a repeated START is generated instead of a STOP condition