Allen Bradley Communication options for OEM product

Hi guys,

I work for a OEM and we make products that has a control panel with a PLC and a touchscreen. We use the same program for each customer,so the customers customize the system by entering some values on the touchscreen. But as such the program is generic. Currently we use Micrologix 1200 and Panelview 600 Std.

Now my question is, if we were to give communication option to customers (to connect our PLC with their PLC or SCADA); which protocol should we choose? I am not very familiar with AB, I know there is ethernet... But the only issue here is we do not want the customer to change our program, neither do we want to make different programs.. We just want to supply some values that they can use.. Is this possible?

Which option would be most demanded? Ethernet?
THanks for your time

That is going to depend upon the customer's SCADA system, and there are MANY of them out there. When I was an OEM, we would just provide a listing of available protocols supported by RSLinx; this put the onus on the end user to provide any protocol conversion hardware. We would also provide a listing of 3rd-party comm modules that would fit in the particular chassis we used for a given system. It really isn't as simple as saying "we can provide ethernet (for example), when there are some proprietary SCADA ethernet protocols: GE FOCAS 1 Ethernet, MODBUS TCP/IP, OMRON FINS Ethernet, Yaskawa MP Ethernet, etc.

Thanks mgvol,

With our Siemens equivalent system (siemens PLC and touchscreen) we have decided to use Profibus. So I was wondering if there was a similar protocol of AB that is more like a standard through which other devices can communicate.

I am more familiar with Siemens on this.. With that I could give the GSD file and mention the addresses. Anyone who has Profibus can tie into our system..

There are Profibus comm modules available, but not for the MicroLogix 1200. ProSoft & SST make chassis-mounted modules for many different protocols for PLC5, SLC and ControLogix. You might want to see if Siemens acn do Ethernet/IP.

What I'd do is get a MicroLogix 1200R and connect the PanelView to its HMI/Programming port, then set the Channel 0 serial port for Modbus RTU Slave.

That's as generic a protocol as anyone could ask for, and when the Channel 0 serial port is set up for that mode nobody can access your program or get into any data you don't want them to.

If your customer is Allen-Bradley savvy, you can connect a 1761-NET-DNI for DeviceNet or a 1761-NET-ENI for EtherNet/IP and give them more access to the controller's native data tables.

I would recommend you stay with the AB protocols available with the Micrologix which will be serial DF1 and Ethernet. The NET-ENI is a gamble if you have too many connections. There is a limit of ethernet and CIP connections on the NET-ENI. Your PV will count as one, the serial port will count as one and the client SCADA will count as one for each I/O server or OPC server accessing the PLC. If you then try to program at the same time you will use another connection and will see unpredictable results from the communications port. The NET-ENI is probably your only answer to get Ethernet unless the MLGX 1200 has onboard Ethenet. If onboard Ethernet is available then go this route. Confirm the Ethernet connection limit though. You can get this from Rockwell and may be on the knowledge base. This port would need to be shared with your PanelView and the Customer HMI/SCADA since there is only one port.

With the values that the client SCADA reads, I recommend you give them a memory map of contiguous registers such as N50:0 through N50:x and your logic writes / moves values into these registers. Do not give them scattered registers based on your logic since this may cause communications overhead issues at the PLC and at the HMI/IO server. Consider carefully remote connection by the customer SCADA to other registers in your PLC if you are held to warranties and performance guarantees. Provide the customer with the memory location and a description of the value that is stored in this address.


Best of luck.