Omron PLC and ethernetmodule question

wwauters

Member
Join Date
Feb 2005
Location
Brussels
Posts
2
Hi,
I am working an a project with 8 Omron CS1G-CPU65 PLC's. Those are linked with controller-link. One PLC is equiped with an ethernetmodule and acts as gateway for the other PLC's. Each PLC has a cycletime of +- 70 ms.
The problem is now that if I want to read datawords from the PLC's from a SCADA on a PC, it takes a lot of time.
The communication between PC and PLC occurs via the Omron Fins Protocol. It uses UDP port 9600 to communicate with the PLC's.
What I found out is that a question from the PC is answerred after by the PLC 200 ms.

To check why it takes so long I've built a test setup with one PLC an a networkcard. After some test It looks like the delay between question and answer is caused by the cycle time.

So lets return to the project-setup (8 PLC's): If I want to question a PLC behind the gateway-PLC, I have to pass the gateway-PLC wich takes 70 ms, then ask the question to the PLC wich takes 70 ms, get the answer back wich takes 140 ms. This results in a total of 280 ms to receive ONE answer. Too long

Does someone knows a setting to use the ethernetmodule independend from the PLC cycle time (a kind of direct memory access)?

Any suggestion is welcome! Thanks a lot, WW
 
Hmmmmm, looks like my question ended up on page 5, after 4 days!!

Perhaps it would be a good idea to split the forums in several sub-topics....

Additional input: The PLC's are CS1G-CPU65 H, and the ethernetcards is a ETN21.

and UP ;-)
 
Have you tried using an OPC server? You can download a free demo from Kepware.
How fast are you looking to retrieve the data?
 
CS1G-CPU65 PLC's

You could replace the main CPU with a CS1H, they are much quicker, and more expensive of course.

Those are linked with controller-link

Are you placing all your required information on the Controller Link network as global data before reading it out of the main PLC? Is Controller Link running at 2 megs? Any slower and their will be added overhead there also.

As you are using Controller Link, why not place a Controller Link PCI card in the PC? I find it works quite well. It would also alleviate the problem of a long scan on the nain processor because you would address each PLC individually. Usually find this a much better system than Ethernet, particularly reading all data out of 1 PLC. A lot cheaper also.

I have one Citect SCADA with a PCI Controller Link card in the computer where Citect kernel is reporting around 15,000 digital reads per second. A couple of hundred word reads as well.

The Controller Link PCI card is also a lot cheaper than a CS1 Ethernet module.
 

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