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I have an RS485 transceiver (datasheet here). Page 8 explains the various pins. I do not appreciate why there are two output pins, namely D_OUT (pin A1) and RO (pin A6).

The first is a "General Purpose Logic Output", the second is the "Receiver Output".

Why are there two different outputs, and what are they respective roles?

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    \$\begingroup\$ Probably downvoted because you would know the answer if you'd read further after "General Purpose Logic Output". \$\endgroup\$
    – stevenvh
    Commented May 21, 2012 at 10:08
  • \$\begingroup\$ I did read further, clearly. I just didn't understand the global picture. \$\endgroup\$
    – Randomblue
    Commented May 21, 2012 at 10:24

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"\$D_{OUT}\$ (Pin A1): General Purpose Logic Output. Logic output connected through isolation path to \$D_{IN}\$ . Under the condition of an isolation communication failure \$D_{OUT}\$ is in a high impedance state."

So this is not a copy of the received signal, but a loopback from the input it gets from your microcontroller. In normal operation conditions it will copy the data you put on the bus, but it won't give you data others are sending. It seems to be used to verify that the isolation communication is in order.

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