There are some things that Rockwell does that make great sense, some that make sense to them when you look at it from a Rockwell Marketing perspective and some that don’t make sense at all. Today I’m going to talk about something in the middle; Ethernet communications for the SLC 5/05. I don’t know how many SLC 5/05 users just don’t understand the Ethernet connectivity on that product but I’d guess it would be a lot.
A lot of people, too many in my opinion, look at that Ethernet port on the 5/05 and think “great – I can tie this into all sorts of things”. Of course, they’re wrong.
Let’s start by examining what Ethernet is. I say it all the time. You should think of it as a pipe. You should think of it as a link from one device to another. Just like my telephone links me to Kow Ming Yeh in Taiwan. Kow Ming and I went to grad school together about a million years ago. But just because I can call Kow Ming’s house in Taiwan that doesn’t mean I can communicate anything. I can call, get a connection but someone that doesn’t speak English answers we’re not going to accomplish anything. All I have is a connection.
So, at the minimum, the Ethernet port on the 5/05 gives you a connection. It just allows you to hook the pipes up between a device and the 5/05. So what travels in that pipe?
That is the key question. The 5/05 supports one protocol, something called PCCC which I think means Programmable Controller Command and Control language. PCCC is a very specific communications protocol that lets other devices read and write the registers of the 5/05. So, any device that wants to transfer information in or out of the data table of a 5/05 must use that protocol.
So, what can do that? Well, ControlLogix and CompactLogix PLCs can do that. RsLinx on a PC can do that and so can some HMIs. There is some non-Rockwell stuff that can do that but not much. We have a number of gateways that you can use to move data in and out of a 5/05 data table. Here’s some of the products that you can get that know how to use this port. If you want to
Move Barcodes into a SLC 5/05 – Our 435NBX is perfect for that. It just loads a set of registers with a barcode or other ASCII string every time a new one arrives.
Move Modbus RTU data in and out of a SLC 5/05 – Our 460ETCMM is a Modbus RTU Master that can connect up to 32 Modbus RTU devices to your 5/05. It links the Modbus Registers and Coils in those RTUs to the data table of the 5/05.
Move Profinet IO data in and out of a SLC 5/05 – Our 460ETCPS is a Profinet IO Device-side device that connects to a Siemens PLC. It allows you to connect the data table of a 5/05 to the I/O data on Profinet IO.
And we have lots more gateways for the SLC 5/05. The common thread among all these devices is that they have to be able to speak that PCCC messaging to transfer the data.
So why is that? Why did RA make this so hard? Well, I usually don’t defend them but in this case I will. In the first place you have to remember when this PLC line was designed. It was way back, long before open protocols. There wasn’t even the concept of open and there weren’t a lot of users or developers that had microprocessor based devices in those days. Most stuff was Discrete I/O based.
And why haven’t they updated it. Because they are eventually going to completely obsolete this line and adding more comms to it kind of defeats that purpose. It might not seem like it but they are doing the right thing.
But as long as you are going to be using these devices, our engineers at RTA will be working hard to make sure you have the right products and tools to keep these devices always be around to help you guys keep this stuff working into the future.