Hi, Looking at the MAX485 functional diagram on page 2 http://ledsee.com/datasheet_ledsee/MAX485.pdf by controlling RE you control the Receiver output "Receiver Output Enable. RO is enabled when RE is low; RO is high impedance when RE is high." If I am not mistaken, It should be as simple as that, if things go well ;-) RE could be set high by a resistor by default until the PIC is ready to tango, which would pull down RE as and when necessary. Cheers, Manu On Sat, Mar 10, 2018 at 10:58 PM, Jim Ruxton wrote: > Just curious how others might handle this scenario. I have 2 RS-485 > signals. I want to route one of the 2 to a UART pin on a PIC. I am > looking at using 2 MAX485 receivers or something similar. These have RX > enable pins that either output the signal or put the output pin into a > high impedance state. I am wondering about tieing the 2 outputs together > and be sure I only have 1 of the 2 outputs enabled. I am just concerned > that on power up the outputs may not be in a high impedance state and > will fight each other until my PIC is fired up completely. My other > option is to join the 2 outputs with series resistors. Since I am going > to have a single optical isolator after the MAX485s I could tie the > outputs together through current limiting resistors going to the > isolator. Or maybe someone has a better suggestion or knows another > rs-485 IC that does this ie. allows the selection of 1 of multiple > inputs. I did a quick mockup of the 2 scenarios only showing the > relevant bits. I am considering here. > https://drive.google.com/open?id=3D1im2HMS2sjCmgZup1q0AzfC9YSY-Z1ew2 > > I would appreciate any thoughts or opinions. > > Jim > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .