DB-9 Pin configuration for Modbus RTU.

Issue

What is the pin configuration for Modbus RTU when using a 9 pin comm port on a BCX controller.

Product Line

Andover Continuum

Environment

  • BCX
  • Modbus RTU

Cause

Connecting a BCX or CX controller to a Modbus RTU device.

Resolution

RS232 connection for a 9 pin BCX comm port.  

BCX Comm 1 (9 Pin)            RJ 45 Connector @ Modbus device

  • Pin 1 CXD        -->                 Pin 1 DTR
  • Pin 7 RTS        -->                 Pin 2 CTS 
  • Pin 4 DTR        -->                 Pin 3 CXD
  • Pin 8 CTS        -->                 Pin 4 RTS
  • Pin 5 GND       -->                 Pin 5 GND
  • Pin 3 TD           -->                 Pin 6 RD
  • Pin 6 DSR        -->                 Pin 7 DSR
  • Pin 2 RD           -->                 Pin 8 TD