ADM2582E: MCU-RXD will receive FFh after MCU-TXD sent Data

Hi all,

I use RS485 transceiver ADM2582E, but I met one problem.

If data rate over 7.5M bps, MCU-RXD will receive one LOW pulse after sent data (Format 8N1), as shown in Figure 1.

But when I setup the UART format to 8N2, the problem has disappeared, as shown in Figure 2.

Does anyone know what the problem is?

The following image was captured from Oscilloscope.

Yellow indicates ADM2582E DE/RE(MCU-TXDEN).
Blue indicates ADM2582E TXD(MCU-TXD).
Purple indicates ADM2582E B-A.
Green indicates ADM2582E RXD (MCU-RXD)

Figure 1.

Figure 2.