What voltage represents the inactive state for UART?

In UART (Universal Asynchronous Receiver/Transmitter) communication, the inactive state is typically represented by a high voltage level, which is commonly 5V. This high state indicates that the line is not actively being driven and remains idle. In UART communication, when data is not being transmitted, the line is held high, which helps ensure reliable communication and minimizes noise interference.

The inactive state being at 5V is significant for several reasons:

1. Standard Logic Levels: Many microcontrollers and digital devices operate at this voltage level for high logic signals, making it compatible with common integrated circuits.

2. Signal Integrity: The high state maintains a stable reference, minimizing the risk of false triggering from noise, which can be more prominent when the voltage is at lower levels.

3. Transmission Start: During transmission, a UART line transitions from this high idle state to a low state (typically 0V or ground) to signal the start of a data frame. This clear distinction between active and inactive states is crucial for proper synchronization during data transfer.

This understanding of the voltage levels used in UART communication helps in designing circuits and ensuring reliable data transfer in automotive and other electronic applications.