Ethernet IP communication faults

[paulB]

We are in the process of designing new machine. This machine will have 1756-L61 processor, 1756-ENBT Network module, 5 remote I/O 1794-AENT adapters, 4 PowerFlex 40 drives with 22-COMM-E cards each, 3 PowerFlex 70 Drives with 20-COMM-E cards each, and 2 PanelView Plus 1000
My question is how to capture communication fault from each of the listed above nodes? Does anyone have suggestions or point to examples.

Thank you,

PaulB.

 

[gscure]

Gsv

You can use a GSV instruction to monitor the module status. This will allow you to know when there is a communication fault with any of the modules (nodes).

 

[paulB]

Thank you for quick reply. Do you know what should I enter for GSV instruction Class Name
Instance Name
Attribute

for each of the nodes: 1794-AENT, 22COMM-E, 20-COMM-E, PANELVIEW PLUS 1000.
What do you recommend, how often it needs to be executed (once per second, more, less):
Thank you,

PaulB.

 

[dmargineau]

The HMI terminal is not part of any RSL5K application file.
In order to automatically verify the CLX to PV+ communications status you will have to periodically "handshake" an HMI application system tag within your Logix Project.
As for any modules within the Logix system application file hardware "tree" visit:

http://literature.rockwellautomation.com/idc/groups/literature/documents/pm/1756-pm015_-en-p.pdf

At page 15 there is an example of monitoring a module's status.

 

[Ken Roach]

Thanks for that link... I hadn't read that Programming Manual and it's nice to see this sort of information, which was previously the provice of Technical Support and the Knowledgebase, documented and published.

I use a simplified mechanism with the GSV instruction, usually run in a subroutine once a second. Instead of a Bit Field Distribute, I divide by 4096 to bit shift the high 4 bits to the low 4 bits of a DINT.

In the attached screenshot, IO_Entry_Status is an INT[x] array (to match the GSV target datatype), IO_Entry_Value is a DINT[x] array, and IO_Status_OK is a BOOL[x] array.

I agree that the simplest way to determine that a PanelView is connected and running its application is to have the PanelView write its own clock to a tag in the logic controller.

FLEX I/O and POINT I/O also have a simpler method when you are using a Rack Optimized connection; the SlotStatusBits word goes to all bits true (for a value of -1) if the connection is broken. That's a quick and dirty method for performing a connection validity check that doesn't require the overhead of a GSV instruction.

 

[gscure]

Great points and ideas!

 

[Ken Roach]

On my most recent project, we went a little overboard and we're reading the Ethernet Link Object out of every I/O Adapter and every port on every Hirschmann RS20 switch every few seconds.

A number of issues were discovered in the way the Ethernet Link Object (an ODVA standard object, Class 0xF6) was implemented in each product. Some support Get Attribute Single, some support Get Attribute All, and each applies the Reset service differently.

The practical result is that we can detect failing Ethernet media before it fails to the point where it will cause network faults. We already detected a mis-wired quick-disconnect this way; it worked fine much of the time, but was giving us "random" I/O disruptions.

I get a lot of "Ethernet is great; it Just Works" proclamations by technology enthusiasts who haven't had to fight a badly-wired or intermittent network. My motto is that "Bandwidth hides a multitude of sins".

 

[dmargineau]

Thanks Ken.

When determining any VFD's communications status we are usually comparing two consequent readings of some parameter/tag which always changes very rapidly, such as the DC Bus voltage.

NEQ = TRUE -> .

EQU = TRUE -> .

 

[paulB]

Ken,

Thank you for example.

Dmargineau,

How would you read bus voltage from Powerflex 40. Is bus voltage changing when drive is not running?

PaulB

 

[Ken Roach]

The bus voltage example would only work well with a drive that supports "DataLinks", like the PowerFlex 7-series.

The GSV method is universally applicable to any device that is in the I/O tree of the ControlLogix, whether it's connected over the backplane, Ethernet, or ControlNet.