Hi,
do you know the exact version of the AC140? I assume it’s not a 8AC140.6y -3, because the -3 variant also has a ethernet interface onboard for online communication.
In general, all variants of 8AC140.xx-y are PLCs plugged into ACOPOS classic. So for that, Automation Studio is the right software to communicate with that PLC.
The RS232 port is able to be used for communication, but all the settings (baudrate, “allowed for online comm.”, a.s.o) can be changed by the software developer who created the project for this PLC.
The default settings of a RS232 online interface on a B&R PLC are: 57600 Baud, Parity Even, 8 Data bits, 1 Stop bit, no additional hardware handshake. So, the RS232 cable must have at least the following connections: RX → TX, TX → RX, GND → GND.
You could check this post to try to determine the right serial parameters (if the online communication is really enabled on the RS232 interface). The post refers to SG3 legacy systems because the’re most often the serial interface was the only one to communicate with the programming environment, but the information is also valid for your type of PLC:
Best regards!