I am confuse with the R1 and R2 function. The "Direct Connection" wire is connected to another transceiver's DE/RE.

When the DE/RE is high, driver is enabled, and when the DE/RE is low, the receiver is enabled. However, the DE/RE line here has 2 resistors.

What state is it in? enter image description here

  • 1
    \$\begingroup\$ I’d be suspicious of the source of this diagram. The datasheet say logic ‘1’ is >= 2.0V, so if direct connection is 5V, then the chip will see logic ‘1’ on its inputs. R1 should be a lower value methinks. \$\endgroup\$
    – Kartman
    Commented Jun 25, 2023 at 1:29
  • \$\begingroup\$ depends on what voltage levels the other driver is sending \$\endgroup\$
    – jsotola
    Commented Jun 25, 2023 at 2:17

1 Answer 1


The resistors are there (most probably) for voltage translation. IC1 is powered with VCC. If direct connection source is powered with a voltage of e.g. two times VCC, then these resistors limit the logic signal voltage to VCC.


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