MSG between a 5/03 and a ML1100 via Ethernet

Hi all,

I have a SLC 5/03 with a 1761-NET-ENI and a ML 1100 on my test bench. I would like to learn messaging between the PLC units. I am a little confused on how to get a message from the 5/03 out to a IP address via the ENI. Can anyone give me some help in that area?
Thanks for any help you can provide,
Chris

Get out the User Manual (1761-UM006) for the 1761-NET-ENI; you're going to need it, especially Chapter 5.

A short summary:

The SLC's serial port only uses DF1 protocol, which has just a DF1 target node address. But it has to send the message to an IP address.

So the Net-ENI has a table of DF1-to-IP address relationships. A message sent with a target of DF1 Node 0 will go to the first IP address, a message sent to DF1 Node 1 will go to the second IP address, and so on.

The IP addresses themselves can be written to the Net-ENI using MSG instructions, or entered in using the Net-ENI configuration utility.

Start by placing the IP address for the MicroLogix 1100 into the IP table of the Net-ENI, then triggering a MSG in the SLC-5/03 whose target is the DF1 Node Address associated with that IP table entry.

Thanks Ken,
I will try that out and see what I get.

One more question, I have a device that I want to communicate Modbus with. If I set up the DH485 port in the 5/03 as a Modbus Master I should be able to go straight out of that port Modbus and not effect the 232 port using DF1, Right? Any tricks to that I should be aware of?

If I set up the DH485 port in the 5/03 as a Modbus Master I should be able to go straight out of that port Modbus and not effect the 232 port using DF1, Right?

Click to expand...

Negative. The Channel 1 port on an SLC-5/03 runs only Data Highway 485 protocol.

Only the Channel 0 serial port can be configured for multiple protocols: DF1, Modbus, and ASCII.

So it isn't just a RS-485 port? What devices work with DH 485? Where is most commonly used?
Thanks for the info Ken!!

Data Highway 485 is sometimes referred to in old A-B documents as "Data Sidewalk".

It's an RS-485 based network that is proprietary to the Allen-Bradley SLC-500 family controller. You'll find it as the only port on the old fixed I/O and SLC-5/01 and 5/02 controllers, and it was used extensively for connecting those controllers to PanelView terminals and to personal computers. Its heyday was really 1988 to about 1998.

If you have to communicate with a Modbus device from this control system, I recommend the Prosoft MVI46-MCM module. It's relatively expensive, but when you solve comms problems with Prosoft they get solved fast and stay solved.

Thanks Ken!! I got the messaging working fine. I have a question about the Error Bit in the control block. What situations causes this bit to be set? I have tried to change the target address and even unplugged the Ethernet cable and it wont set the ER bit. Makes me wonder what that is used for.

The .ER bit should become true when the message times out.

Are you sure you're not re-triggering it in logic ?

I was!! I had the DN and ER bit in parallel with the message enable unlatch. So every time I got a ER I would just reset the message and try again. I attached my logic.

What is a good way to handle errors during messaging? Do you use a counter and have some alarm logic after so many errors?

One other question I had about the DH485, I see there is a converter (1747-UIC) that will convert USB to DH485. That can be used for programming, correct? If I set the CH.0 to Modbus Master I can no longer use CH.0 for programming, right? I want to make sure I can get to the processor with RSL500 I make that change.

One last question: Will the ENI do Modbus TCP/IP? I would like to see if I can talk to my demo Flow Computer via TCP/IP.

Thanks for all your help Ken!!

Sorry I posted the wrong logic.

Error handling and message sequencing is actually a moderately complex topic.

Using a Counter to count the /ER bits is a good way of making background
comms problems apparent. It's a good addition to having a Diagnostic Data File configured for each channel.

The 1747-UIC is a good way to get online through Channel 1 when Channel 0 is being used for something like Modbus or ASCII. If you "lock yourself out" of Channel 0, you need to either use Channel 1 or pull the battery and drain the capacitor to reset the controller back to defaults.

The 1761-NET-ENI doesn't do any Modbus/TCP functions.

A related device, the Digi One IAP, supports both Modbus/TCP and EtherNet/IP and DF1. It's a very flexible device, but I find it more complex to understand and configure than the Net-ENI. It has a reputation for better performance (more TCP connections) and reliability than the Net-ENI.

I'm not sure if the Digi One IAP will do what you are doing here, the redirection of a DF1 message to an IP address.