RS232, RS232/485 and USB Ports of Ace PLC

All Ace PLCs have an USB port and certain Ace PLCs have RS232 ports or configurable RS232/485 ports. RS232/485 ports are commonly used for interfacing hardware HMI panels 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 Custom communications mode to communicate to any device that has an RS232/485 port.

USB port can be also configured as Modbus Slave like the RS232/485 ports !

RS485 ports are commonly used in multi unit systems and for longer distance communictions.

Ace PLC RS232 ports have three pin connectors. The illustration on the right shows the connections.
• Signal ground
• PLC transmit (must be connected to the receive pin of the connected device)
• PLC receive (must be connected to the transmit pin of the connected device)


Some Ace PLCs 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 and 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.

Find this information in the Ace User Guide