Again, only the serial RXD and TXD are converted to those levels. Again, if you would like this type of functionality in RS-485, you'll must implement it your self. Hi, I'm not fairly positive but when I remember good all UART's are in TTL customary - 3,3 V I assume - and only one is in RS-232 commonplace. In the standard configuration, the RS-485 bus is in an undefined state when there are no lively transmitters.