ISO3082: 1st A&B output pulse after enable driver

Hi,

In the test of ISO3082, we obverse both output A&B are driven to "low" at the 1st bit after enable driver. 

If the device work properly, when D = '0'

A='0', B='1'

But, from capture, when D = '0', after enable driver with D='1'

A='0', B='0' then turn to '1' after 0.8us. 

Is this the correct behavior for ISO3082?

Schematic: There is a modification on board R36 = R42 = 680 Ohm.

Waveform: CH1: RS485_TX(D); CH2: RS485-(B); CH3: RS485+(A); CH4: S485_EN(DE)

Thanks.

Zhou