The synchronization between master and slave is achieved by recognizable START condition and STOP condition, which determine the beginning and the end of a transaction. The bus is initially idle, with both signals at the high logic state when all the participants are idling.
A START condition describes the beginning of the transmission, and it is the only case when SDA is pulled low before SCL by the master. The special condition communicates to slaves and other masters on the bus that a transaction is initiated. A STOP condition can be identified by the SDA transaction from low to high level, while the SCL remains high. After a STOP condition, the bus is idle again, and initiating communication is only possible if a ...
