When I change /RE High to Low,RXD OUT put became Low (about 260ns).
Could you tell me a reason?
The bus termination of 50 ohm is too low.
The RS-485 transceiver can drive a minimum 54 ohms.
For your specific question - can you please add a 1 nF capacitor between the A and B bus lines.…
Adding 1nF of capacitance is equivalent to adding a longer bus cable. 20 meters of added cable for example.
The 1 nF capacitance should not limit your data rate, especially as you are operating…