watchdog timer maximum value help

[jvalle]

Can someone please help me with this? I have three plc 5 processors that sometimes have communication problems. I would like to create a watchdog timer to show the status of each processor to processor communication on the HMI screen. Along with displaying the actual watchdog timers I would like to display the maximum value that the watchdog timer reached. How would I go about doing this? Is there an easy way?

Thanks
Joel

 

[spaderkung]

Perhaps defining the problem better would help? Will there be 25 WDTs, and what happens when they roll over?

 

[jvalle]

The three processors are linked together by DH+. I am sending read and write messages between all of them. Sometimes the DH+ connections get dirty and the communication either slows down or stops. I just need to know when this happens.

 

[Ron Beaufort]

Greetings Joel ...



I know that this won’t fully answer your question, but it might be a piece of the puzzle to get you started ...



the picture below is from the “Comms” tab under the “Processor Status” feature ... each PLC on the DH+ “knows” about the other active PLCs on the network ... a “1” on this table means that a station is “active” - that position on the table will turn to a “0” whenever the related PLC drops off of the network ...

bring up this screen on your system and you should be able to identify the active nodes ... if you right-click on any of the boxes, RSLogix5 will give you the address of the bit ... then you can program each PLC to examine these bits and respond appropriately if one of its neighbors drops out ...



hope this helps ...

 

[jvalle]

Hello Ron.....


This is very helpful. Right now I have on my HMI screens the "Max Scan" and the "Last Scan" of each processor. I want to do the same with the communication between the processors. I may need to do some of this within the HMI on memory tags. As for the status bits, this will help me out quite a bit. Thanks again Ron!

 

[OkiePC]

You may also want to investigate the channel status files for the DH+ channels on each of the procesors. It can reveal much about the DH+ connections and you can view those entries on your HMI.

You must assign a data table to the channel diagnostic in your channel configuration (if not already assigned), then you can view the data formatted by RSLogix5 when you look at channel status. You can assign coments to the individual elements and use them in your HMI/PLC apps.

I don't have the software to give you better details...only using SLC and C-Logix now.

Paul

 

[Oakley]

Doesn't the DH+ table show a processor even though it may be in program mode?

I always use a handshake between PLC's to determine if they are running. In addition, I do a handshake with the HMI.


Question: Is your messaging between nodes all grouped in a single group of data registers? Is your messaging conditionalized?