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Wiring diagram of the serial RS232/RS485

Certain ACE have RS232 ports or configurable RS232/485 ports.

  • RS232 ports are commonly used for interfacing HMI and other devices through Modbus RTU communications. They are also commonly used to interface cellular transceivers for internet of things applications and can be used in ASCII communications mode to communicate to any device that has an RS232 port.
  • RS485 ports are commonly used in multi-unit systems and for longer distance communictions.
  • Our serial port is a true standard RS232/485. It is NOT a TTL level (0 / 5 VDC) : A logic high is represented by a negative voltage -5 while a logic low transmits a positive voltage +5 V.
ACE RS232 ports have three pin connectors. The illustration on the right shows the connections.

  • Signal ground
  • TX (must be connected to RX pin of the connected device)
  • RX (must be connected to TX pin of the connected device)
Some ACE have serial ports that can be configured as either RS232 or RS485. When configured as RS232, the connections are identical to the connections shown for the dedicated RS232 ports.
If the port is configured for RS485, the two connections used are

  • the + (or A), on the same pin as the RS232’s RX
  • the – (or B), on the middle pin or RS232’s TX pin.

The ground can be connected to the cable shield. However, the shield should only be connected at one end of the cable.

Wirring of the HMI serial port

HMI D-sub 9 pins
View from outside
1    2    3    4    5
6    7    8    9

RS232, RS485 and RS422 pins

Wirring from the HMI to the RS232 3 position plug of the ACE

RS-485 network wiring

Wirring issue

If you don’t see this indicator light blinking on your HMI, it’s probably a wiring cable problem.