Difference Between DCE and DTE Serial Connections

Difference Between DTE and DCE Serial Connections

Which serial connection is it…DCE or DTE?

We often get asked the question “What’s difference between DCE and DTE Serial Connections?”. Below we have compiled a chart to help you identify the difference between the two connections in RS-232 Interface.

Please note that not all manufacturers follow RS-232 Standards. One or more characteristics may not match the chart

It is a DCE
RS-232 Interface…

It is a DTE
RS-232 Interface…

  • If it outputs on Pin 3 and Inputs on Pin 2
  • If it’s a modem
  • If DSR (pin 6), and /or CTS (Pin 5), and/or DCD (Pin 8) are High
  • If it Raises RI (pin 22) to initiate a Handshake
  • If it Raises DSR (pin 6), and/or CTS (pin 5), and/or DCD (pin 8) in return for a Raised DTR (pin 20) and/or RTS (pin 4)
  • If it uses a “Straight Through” cable to a terminal
  • If it uses a “Cross-over” (Null Modem) cable to connect to a modem
  • If it outputs on Pin 2 and Inputs on Pin 3
  • If it’s a Terminal or Printer
  • If DTR (pin 20) and/or RTS (pin 4) are High
  • If it Receives RI (pin 22) to initiate a Handshake
  • If it Drops and Re-raises DTR (pin 20) after a Drop of DCD (pin 8)
  • If Busy (pin 25) is High
  • If it uses a “Straight Through” cable to a modem
  • If it uses a “Cross-over” (Null Modem) cable to connect to a Terminal