in a Bidirectional Transceiver 485 IC which is 3-State Driver and Receiver Outputs the RE (Receiver enable) & DE (Driver enable) pins control communication direction
when you sending data active the DE pin (High) to transfer data to bus
when you receiving data active the RE pin (Low) to get data from bus
DE & RE Propagation delay time, standby-to-active (hi or low) = 3.3us max with RL=110 Ohm , RE=3V
DE & RE disable time is quick (17ns@15pF) but depends on cable capacitance.