JAJSDP5D February 2016 – March 2018 LM36273
PRODUCTION DATA.
One data bit is transferred during each clock pulse. Data is sampled during the high state of the SCL. Consequently, throughout the clock’s high period, the data remains stable. Any changes on the SDA line during the high state of the SCL and in the middle of a transaction, aborts the current transaction. New data is sent during the low SCL state. This protocol permits a single data line to transfer both command/control information and data using the synchronous serial clock.
Each data transaction is composed of a start condition, a number of byte transfers (set by the software), and a stop condition to terminate the transaction. Every byte written to the SDA bus must be 8 bits long and is transferred with the most significant bit first. After each byte, an acknowledge signal must follow. The following sections provide further details of this process.
The Master device on the bus always generates the start and stop conditions (control codes). After a Start Condition is generated, the bus is considered busy, and it retains this status until a certain time after a stop condition is generated. A high-to-low transition of the data line (SDA) while the clock (SCL) is high indicates a start condition. A low-to-high transition of the SDA line while the SCL is high indicates a stop condition.
In addition to the first start condition, a repeated start condition can be generated in the middle of a transaction. This allows another device to be accessed, or a register read cycle.