AC500 Modbus RTU
I would like to ask regarding Modbus RTU Connection on the AC500 controller.
currently I have an existing connection of RS485 2-wire (Pins 2,3 & 7) used for a device. But I need to connect another modbus RTU device onto the AC500 controller, can I utilize the RS232 connection port to connect another slave or I can only multi drop the modbus from existing device?
Please define better your question and the type of the CPU.
If you are asking if it is possible to use one COM for both RS232 and RS485 simultaneous, I think that is not possible.
But you can configure COM1 for RS485 and COM2 for RS232 (depends on the type of the CPU - only AC500 for RS232)
Also you can use COM_SET_PROT function block to define the protocol for the COM port from the program (software) if you configure the COM port as Multi, but only one protocol to one COM at a moment is possible (not simultaneous)
As a solution, you can install RS485 to RS232 converter and connect the new RS232 slave to your existing line RS485, of course with different slave address
Please look in the help:
1. AC500 CPUs PM57x, PM58x and PM59x are equipped with the two interfaces COM1 and COM2 which can be operated as RS-232 and RS-485
2. AC500 PM55x and PM56x CPUs are equipped with two interfaces COM1 and COM2 (optional) which can be operated as RS-485 only
I believe the RTS-Control parameter under COM-Modbus settings determines whether RS232 or RS485 standard is active on the COM port.
In case your slave supports only RS232, you may have to use an RS232 to RS485 converter and connect it in a multidrop fashion. If the slave supports RS485 as well, then device can be connected to the RS485 line as a daisy chain or multidrop node.