Can I connect MODBUS RS485 Device to AC800M COM3 Port?
I have PM9C energy meter, and I want this device to connect Com3 Port on AC800M. PM9C support 2-wire (and 1 gnd) RS485. Can I connect this device to Com3 Port without using converter?
I did some research and I found the detailed explanation of Com3 and its pin description. I used RD(6), TD(3) and 0V(4,5) pins and connected them to PM9C. However, it didn't work. Is it a problem other pins are empty? Should I do any configuration on the DCS side in hardware conf or in the application? I set the baud rate etc. But there is no device under Com3. Should I add PPP or something else?
I am really confused. Can anyone help? Can I connect this device to Com3 Port without converter? If yes, how?
Voted best answer
AC800 M controllers like PM861, PM864 and PM866 or controllers with TP830 base COM3 can be used for serial communication.
We cannot connect to COM3 port directly if the Modbus Slave device is RS485. COM3 on TP830 is a RS232C port. You cam find more details in 3BSE036351-510, Controller hardware manual.
You can use standard ABB TK853 cable provided pin configuration on RS232/RS485 converter matches with this.
In one of our project i used the below configuration (CI853 module) to match with RS232/RS485 converter.
You need to do small configuration in control builder hardware too. Insert modbus type under COM3. To get this type you have insert MOodBusHWLib into your project project and connect that to controller as well as connected libraries.
Configure the setting under COM3 port, Baud Rate, Parity, Data Bits etc..
The above needs to be done apart from your application configuration using MBConnect and other blocks.
I suggest you to use Modscan (software) for troubleshooting at converter side.