One of the remote HMI is the Modbus slave here. Toolbox ST V4.6.9C is installed in this HMI and workstation ST is running in it. Yokogawa ALE111 card is the master here. Not able to establish communication. ST status monitor shows that "Modbus is running but not responding to status requests from workstation ST". HMI can go online without any problem. Can ping from both side. Please suggest solution/troubleshooting method.

Regards,
SM

 

SM,

Is this communication link something you're trying to establish for the first time, or something that was working in the past and has stopped working?

 

CSA,

> Is this communication link something you're trying to establish for the first time,
> or something that was working in the past and has stopped working?

It was for the first time. Anyway this particular issue solved now. It was issue with the Modbus address range. It was 40001, 40002 etc. corrected to 00001, 00002 etc. and the issue solved.

But now I came across a new issue. When I disconnect the ALE111 card cable from the HMI PC and connect through the Ethernet switch Catalyst 2960-s (As per original network drawing, the ALE111 card should be connected through ethernet switch Catalyst 2960-s; I connected directly to the HMI PC only for the purpose of troubleshooting) it stops communicating. I noticed another thing that if we install one additional switch between Catalyst switch and ALE111 it communicates.

Any clue why ALE111 can't talk to the HMI through the catalyst 2960-s?

Thanks,
SM

 

SM,

I have no clue about the networking issue concerning the managed switch. Are you sure you're plugged into a PDH port? If the ALE111 appears on the original Network drawings, it should also indicate which port it should be plugged into. Some managed switch set-ups required certain NICs/IP addresses to be connected to certain ports (for network monitoring and troubleshooting). That's about the only thing I can think of.

 

Hi CSA,

Yes the port used is correct as per the network drawing. Today I found one peculiar thing; I opened the switch configuration text file and found that the speed is "GigabitEthernet". See the copy paste from configuration file below. And the ALE111 card specification is 10BASE-T. I think this could be the reason. What do you think CSA?<pre>
interface GigabitEthernet1/0/1
description PDH
switchport access vlan 201
switchport mode access
no logging event link-status
speed 100
srr-queue bandwidth share 10 50 15 35
mls qos trust dscp
storm-control broadcast level 50.00 20.00
storm-control multicast level 5.00 2.00
spanning-tree portfast
service-policy input PDH_INPUT_POLICY""</pre>

 

SM,

If this is a GE-provided managed switch, I would be EXTREMELY reluctant to change any settings without GE's concurrence.

If I understand Ethernet networking, something that is Gigabit compliant is also "backwards"-compliant, so it would work with 10-Base-T cards.

Are you sure you're on the PDH, and using a PDH IP address for the NIC and a PDH port? Because, if you were able to get it to work "directly" with the Historian HMI (I presume you were using a cross-over cable?) it should work through the switch--presuming the switch allows "spare" ports to be used. Again, some GE-provided switches were configured to only allow certain NICs to be connected to certain ports (as part of an optional networking monitoring scheme), so this could be a problem.

Hope this helps!

(Remember--in the GE scheme of things, external controllers/PCs/HMIs aren't allowed on the UDH, they must communicate with any Mark VI via an HMI over the PDH, and then the HMI would obtain/provide the information from the Mark VI. So, any communication must be done via the PDH and through an HMI. (Historians are the exception to this rule.))

 

> file below. And the ALE111 card specification is 10BASE-T. I speed 100

This is almost trivial, but I have worked long hours many times because something trivial when over my head.

Change the "speed 100" to "speed 10" in the 2960 switch configuration, or remove the command and let it auto-negotiate but auto sometimes does not work depending on the network setup and other details.

If you don't know how to change it, the cisco website has all the documentation you need to figure it out, and since you were able to open the configuration, you should have no problems.

 

Dear all,

The issue solved.

It was the speed and mode setting mismatch inside cisco created the trouble.

Changed the speed to 10 Base T and mode to Half duplex of the Cisco switch ports to match it with the ALE111 specification.
And the communication started.

Thanks for your inputs.
SM

 

SM,

Thanks very much for the feedback!