MSG read from Micrologix ENI to SLC5/05

ArcReactorKC

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Jun 2021
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So I have a micrologix 1500 on network through an ENI. I need to read an integer from it to my SLC5/05 so I can stop pumps when the remote tank is at level.

It occurs to me I have never done this before. As the micrologix is actually being communicated with through serial and not ethernet I'm unsure how to set up the read MSG command. I thought about it being possible for a WRITE MSG but the micrologix of course cannot send to an IP address from a serial port.

Any bright ideas?
 
It will be easiest to put a MSG instruction configured to perform a Data Table Read in the SLC-5/05. You will use the IP address of the Net-ENI as the target address, treating it just like another SLC-5/05.

If your SLC-5/05 is more than about 20 years old, it might have only the original CSPv4 A-B Ethernet proprietary protocol. After 2000 or so, all the SLC's were built as "dual stack" firmware that supported both EtherNet/IP messaging and CSPv4.

The Net-ENI supports only EtherNet/IP, so if you can see them both with an RSLinx "EtherNet/IP" driver then they are definitely compatible.

For the MicroLogix 1500 to initiate the message, you would have to configure a DF1 Node / IP Address "routing table" in the Net-ENI, which is described in its user manual and the Net-ENI Configuration Utility.

To use the routing table, the MSG instruction configured in the MicroLogix would be addressed to a DF1 address in the 0-49 range, which the Net-ENI would then translate to an IP address from that routing table, and forward on the message (and its reply).

If you want to do this with maximum difficulty, you don't use the Configuration Utility and instead set up the routing table by sending messages to a range of DF1 addresses (100-149) from the MicroLogix user program.
 
Ah genius! Use the ENI configuration software. The fact I didn't even stop to think about that before making a post raises question of my own faculties!


Thank you.
 
I know this goes without saying, but I see this 'overlooked' many times. If you're going to control a process with data from a remote controller, program it in such a way that if the data is not reliable, it won't run. Heartbeat timers and broken line monitoring is the way.
 
We always read words minimum

First one is a heartbeat that is always counting
If it stops moving for x seconds it alarms & stops the process

Also you can calculate communication speed
Subtract first clock read from second
 
One good idea I learned is we never allow write commands
Only read commands are used

This way a PLC is only requesting information it wants
It is not broadcasting data that may not be desired

Somebody could make a mistake with a write command
& send data to a PLC that does not want it & really mess things up

It is virtually impossible to troubleshoot a random PLC sending a
e-stop command to a PLC 3 buildings away one time per week
 
There is a heartbeat along with the relevant data. This is just to enable a separate waste water process when one of the tanks is high to keep from processing water that has to much solid content.

Dayvieboy agreed, I am not a fan of writing data, I will be reading data from the remote I/O so the master in this scenario can write to it's local I/O.

Widelto. I would love to not have an ENI in this system. However it is an inherited kludged together setup and not a lot of $$$ to throw at it. I'm going to make it operate with current hardware. However it has been noted that this is all outdated and on borrowed time. The "master" in this system is a SLC 5/05. It's days are numbered and I think that number might be down to the double digits.
 

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