Can the ADM2582E not have pull-up/pull-down resistors?

Biasing resistors are not required for RS-485 failsafe. The ADM2587E/ADM2582E has Open- and short-circuit, fail-safe receiver inputs. The receiver input threshold voltage is offset at -30 mV, so that RO = 1 output high on open and short circuit buses.

The biasing resistors can be added to provide additional noise immunity. They are not required, but an optional extra.

Using biasing on the network will increase the DC bus voltage offset.

See page 6 of AN-960: http://www.analog.com/media/en/technical-documentation/application-notes/AN-960.pdf   

The examples on page 6 mean that the DC bus voltage will be offset by greater than +200 mV.

Bus biasing will increase noise immunity, so in a bus idle condition ~ 0V there will be no spurious data on the RS-485 receiver output.

Dear team, I would like to consult this question.
Vcc=3.3v, Visoout=Visoin=3.3v can be obtained. To enhance system robustness, the bias resistor R1 = R2 = 960 ohms (since Visout = visoin = 3.3v).

Hi lijie,

Yes you can use 960 ohm biasing resistors if required in your application.

Best regards,

Richard