Skip to content
Ask A Question
  • There are no suggestions because the search field is empty.

Omron Ethernet TOP Server talking to more than 1 Omron PLC

Symptoms: Periodically communications slows down to the point that the only way to solve it seems to be to redeploy the entire application in ArchestrA which is causing a lot of pain.

- Currently multiple PLCs and all under one channel in the Server configuration.

For Omron Ethernet Communications

  1. Communication to multiple physical devices from the same channel when using Ethernet in the OPC server is not effective since the port number and adapter are configured at the channel level and Omron Communications requires the Port number and IP combination to be unique in order to allow parallel communications and keep sends and receives synchronized.  More than one device on a single channel only works if you were to set your client up to communicate to one PLC at a time.
  2. In order to communicate to the different devices across multiple TOP Server channels, you must either use a unique port number for each channel (and configure this in each PLC - see example below), or use the same port number, but configure each channel to use a unique network adapter and IP (which can be accomplished using multihoming -setting up different IP addresses on the same PC Ethernet card- this is covered in the driver help file under multihoming). 
This port issue is an Omron limitation.  In Omron communications every request from a particular IP address must come from a specific port each time.  In normal Ethernet communications the PC operating system assigns a port based on a list of available ports and the return message is sent back to this port which allows parallel threads of communications.  In Omron communications the reply message is sent to a specific port (9600 by default) and will only listen for messages from ports configured in the PLC.  If you use the same IP address and port for more than one PLC you can't do multi-threads of communication because all communication is going through a single Ethernet Port even if you have a unique channel for each device. 

 

Note a) If you do have all the PLCs under a single channel, if one PLC was having timeouts or slow downs in comms, that would slow down comms to all other PLCs on that channel.... where if you put each PLC in it's own channel, problems on one PLC do not affect other PLCs.  This behavior is true of for all drivers as using a single channel results in single threaded communications. 

Note b) If you have created multiple devices under one channel and need to change this to one device per channel now, keep in mind you can keep the device names, and then setup ALIAS names in TOP Server that make those independent devices "appear" to the topics that Wonderware or an OPC Client is talking to, as if they are still under the same channel. This can save a lot of potential rework.  

Note c) If the PC is on a different network then the PLCs, it is critical that the last number of the PC IP address does not match the last number of the IP address of any of the PLCs you are communicating with.  For example, if the PLC has the IP address of 192.111.167.20 and the PC has the address of 10.21.15.20, the communications will fail because the last number of 20 matches. This is a limitations of the Omron PLC Ethernet communications. 

Note d) To prevent problems when using multiple channels, You need to change the port settings on the PLCs or multihome your Ethernet Card (this is covered in the help file and is the preferred method as it requires no change in the PLC).  There is no need to involve table routing as you aren't bridging.  With the Programming software change the listening port to a unique number for each PLC and match this in the TOP Server Channel configuration.  

From the help file:

"Port: Specify the port number to be used by the devices on the local Ethernet network. FINS requires that the source and destination port number be the same. The valid range is 1 to 65535. The default setting is 9600.

 

Users can create multiple channels in the server that utilize a unique port number to optimize communication performance. Examples are as follows:

  • Channel1.device1 uses port 9601.
  • Channel2.device2 uses port 9602.
  • CX programmer uses port 9600."