Communications-Contrologix to Micro

Hello All,

I have an existing installation using a Contrologix main PLC talking to 3 remote Micrologix 12 or 1500 PLC's. They communicate over serial radios. Presently the main site has a Prosoft Prolinx Ethernet to Serial adpater. I have the SLC/PLC mapping set-up to communicate to the remote PLC and there associated data files.

I am experiencing intermittent communication loss, every week, for some length of time. The RX lights on the remote radios are lit almost continuously. The RX/TX lights on the Micro only appear to light when the PLC activates communication. Is there a way that I can use the good old MSG instruction with a NET-ENI module at the main site, and implement timed and controlled activations of the communications. It appears that the prolinx is hammering the remote radios. I am not familiar with the prolinx and would like to switch to the NET-ENI module if possible. Do I still use the SLC/PLC mapping even if I activate the read/write messages from the main site??

Any insight would be greatly appreciated!!

Any other information needed to help you guys out???

I really need some help, no one seems to respond to my questions, lol.

Am I being unclear??

Explain more about this architecture. I understand about the ControlLogix at the main site and MicroLogix 1200 and 1500 controllers at the remote sites, but I don't completely understand the protocol or the ProLinx role.

Does the ProLinx act as a DF1 Half Duplex Master, polling the MicroLogix controllers ? Or is the ProLinx just waiting for DF1 Full Duplex messages from the MicroLogix controllers, and translating those to EtherNet/IP for the ControlLogix ?

I am more familiar with these kind of systems when the ControlLogix serial port is connected to a master radio, and the MicroLogix serial ports are connected to slave radios.

Describe the part number and the configuration of the ProLinx, and describe the protocol and programming of the MicroLogix controllers. It's also important to learn how the system recovers from the communication loss.

Thanks for replying Ken!


Ok, to be more specific we are using micro 1500 LRP series C. They are set-up for DF-1 half duplex slave. I believe the Prolinx is set-up to be the DF-1 Half duplex master.

There are no message instructions in any of the PLC's, from what I am told the Prolinx does all the work. Now, the guy that set it up said he tried reducing the polling rate/or baud, I think he was confused. He said after reducing he started getting comm fails. I think he just reduced the baud rate and then the whole thing quit working.(I am coming in after the fact to try and get it working properly). After a period of time with comm loss to the remote sites, they will resume as normal with no intervention. The radios are radiolinx, not exactly sure how they are set-up, as they have been installed for some time now.

My question is as follows: I have used a Controllogix to talk to 2 micros before, but I used the AB ETH to RS232 (NET-ENI???) convertor on each PLC. So I had main IP and 2 remote IP addresses, then configured the MSG instruction for multi-hop.

What I am not sure about with this setup is, if I use a NET-ENI???? module off the controllogix, then connect that to the serial port of the radio, how do I separate the signals from the remote sites. Would I use the same IP address in the MSG instructions for all remote PLC's but modify the path somehow to include which node each PLC is designated???

Or is my best bet to find a way to get the prolinx to reduce its poll rate?

I have attached a few pages from the Prolinx manual, and I could add the programs if needed, the main Program is a mess though.

The 1761-NET-ENI only uses DF1 Full Duplex on it's serial port, so it's not appropriate for use with modems or with Half Duplex protocol.

You mentioned that the "RX lights on the remote radios are lit almost continuously" during the "comm fail" period.

Let's figure out precisely what these LED's mean. Do they indicate that the modem is receiving data over the radio side, or do they indicate that the modem is receiving data on it's serial side ?

Can you post the configuration file for the ProLinx ?

The RX LED is lit all the time not just during Comm Fail. I do not have access to the configuration file at this time. I may be able to grab it the next time I goto site.

I think but I may be wrong that the RX light on the remote radios being on all the time indicate usually indicate a full duplex setup. Conversely the TX light on the master will be on all the time. I think the carrier signal only is being transmitted. Regards Alan Case