The R of the 485 interface chip is the receiving end, and the communication information from the bus is converted into a level signal and sent to the MCU through the R end. T is the sending end, the information to be sent by the MCU is sent to the 485 interface chip through the T end, and then converted into a balanced differential signal by the interface chip.
Please note that the pin definition of the interface chip should be read in detail when using, and the R of some 485 interface chips or communication modules is the sending end, which is in accordance with the terminal MCU RXD.