I'm using the UART in a multi-processor application. How much time do I have to decode my device address prior to clearing SM2 / MCE before data is lost?
Answer
The SM2 / MCE bit is sampled, and decisions based on it are made, at the time the UART RX hardware samples the 9th data bit (or STOP bit in 8-bit data mode). If the bit is cleared any time before the 9th data bit is sampled, then the logic state of the 9th bit is not used to accept or ignore the received byte.
SM2 / MCE Timing Behavior