The I2C bus operates with two signal lines: SDA (Serial Data Line) and SCL (Serial Clock Line). When both lines are high, the bus is in an idle state. During this time, all devices on the bus are in a high-impedance state, allowing the pull-up resistors to maintain the high voltage levels on both lines.
A start condition is generated when the SCL line is high, and the SDA line transitions from high to low. This negative edge signifies the beginning of a data transfer and is initiated by the master device. The start condition must occur only when the bus is in an idle state, ensuring that no other device is using the bus at that moment.
After a data transfer is completed, if the master wants to continue communicating without releasing the bus, it can issue a repeated start (Sr) condition. This condition acts as both the end of the previous transmission and the beginning of a new one, allowing the master to retain control of the bus. A stop condition occurs when the SCL line is high and the SDA line transitions from low to high, marking the end of a communication session.
It's important to note that both the start and stop conditions are timing signals, not level-based signals. They are actively generated by the master and do not follow the same rules as data bits. Unlike data, these signals can be recognized more easily because they are designed to stand out, making them distinguishable from regular data transfers.
Data is transmitted serially over the I2C bus, with each bit synchronized by the clock signal on the SCL line. The SDA line must remain stable during the high period of the SCL pulse. A low level on SDA represents a logic 0, while a high level represents a logic 1. Changes in SDA can only occur when the SCL line is low.
Each byte of data is followed by an acknowledgment (ACK) or non-acknowledgment (NACK) signal. The receiver pulls the SDA line low for an ACK, indicating successful reception, or leaves it high for a NACK, indicating an error or failure. The master may also insert a wait time by holding the SCL line low, allowing the slave to process data before continuing the transmission.
In cases of bus contention, where multiple masters attempt to access the bus simultaneously, arbitration takes place on the SDA line. If a master sends a high level while another sends a low level, the one sending high will lose arbitration and disable its output. This ensures that only one master controls the bus at any given time, preventing data collisions.
Clock synchronization on the I2C bus is managed through the logical AND of all devices connected to the SCL line. The clock pulses are determined by the slowest device, ensuring all participants stay in sync. This allows for reliable communication even when devices operate at different speeds.
Overall, the I2C protocol provides a robust and efficient method for communication between devices, with clear definitions for start and stop conditions, data transfer, acknowledgment, and arbitration, making it widely used in embedded systems and microcontroller applications.
Ceramic Insulator,Ceramic Electrical Insulators,Ceramic Standoff Insulators,Ceramic Isolators
Yixing Guangming Special Ceramics Co.,Ltd , https://www.yxgmtc.com