I am implementing a semi-duplex multimaster communication (based on RS-485), so before start sending message I need to know if any other node isn't transmitting anything. As far as I see the first information about any received transmission is UARTSR.DTF bit, which is set after reception of full byte.
I need to know if UART has started a reception (start bit received) or if any activity appears on RX line.
Checking RX line state is not sufficient, because I can miss the moment when it is in '0' state. I'd rather avoid to engage external interrupts too, because it would use significant time of CPU and make solution very complex.
