MAX3485/MAX485 Low-Power Shutdown Mode
Just bring RE high and DE low. From the datasheet:


  RO is enabled when RE is low; RO is high impedance when RE is high.


and


  The driver outputs are enabled by bringing DE high. They are high impedance when DE is low.


So when RE is driven high and DE is driven low simultaneously the receiver and transmitter will be in high impedance state.