I have used an exception when using ADM485E communication. Some questions I would like to ask.
(1) ADM485E supports open fail safe function in RX mode in the datasheet, and the output is high level.
When all RS-485 driver is RX mode,the AB input floating, the output is low. But this state will cause the RS-485 start bit to be indeterminate.
Why output status does not meet the datasheet ?
(2) The RS485 fail safe biasing circuit , R1 & R2 resistance installed on the master side or slave side?