OkiePC
Lifetime Supporting Member
I know how connections are created, but how are they released?
Problem SLC: 1741-L551B OS 501, FRN 8
Ethernet Daughterboard Series 2, FRN 59
I don't know if this is a factor, but yesterday there was some maintenace done on a UPS system that supplies power to many PCs, switches and even some PLCs on our controls LAN. They yanked power on a bunch of stuff at various times.
Today, I needed to make some changes to some messaging between two of the SLC 5/05s. I edited (online) a message read from one SLC to the problem SLC. I moved the target (problem) PLC addresses and changed the message length from 2 to 10, and kept the same control block.
After I finished the edits, I noticed that some other messages in the Problem SLC were erroring out. The error message was something like 'already at maximum connections', so I opened the CH1 diagnostics and found that there were 16 connections in use...that can't be right...
So, I did some online editing to temporarily halt all of the messages (four) between the two PLCs by deleting the rungs and then testing the edits. This did not make any difference...even after waiting for about 30 minutes...I still don't know what tells the SLC to begin releasing connections...There is still another SLC that I could not get to which was also still reading from it, but that should only be one connection.
So, I put the SLC in program mode and back to remote run using RSLogix...no difference. Then I uploaded and saved the program, went offline, and then went to the channel connections tab and pushed the clear button to zero out all the counts. I then downloaded the program and put it back in run mode. The connections jumped right back to 16.
Finally, to clear this up, I went to the SLC and cycled power. Now we are back to the normal 6-7 connections. Apparently the ethernet daughtercard holds onto connections even when the SLC is in program mode...which makes sense, cause it still needs to be able to talk to other stuff...
So, this is more informational for others, but I am still curious about the mechanism that would allow those extra connections to be created and then released. I am not 100% sure the editing of the message instructions had anything to do with it, since I did not look for any errors before I started making those edits, and the edits were done in the other PLC, and continued to work even while the connections were maxed out.
Thanks for any insight about how these mysterious connections actually work.
Paul
Problem SLC: 1741-L551B OS 501, FRN 8
Ethernet Daughterboard Series 2, FRN 59
I don't know if this is a factor, but yesterday there was some maintenace done on a UPS system that supplies power to many PCs, switches and even some PLCs on our controls LAN. They yanked power on a bunch of stuff at various times.
Today, I needed to make some changes to some messaging between two of the SLC 5/05s. I edited (online) a message read from one SLC to the problem SLC. I moved the target (problem) PLC addresses and changed the message length from 2 to 10, and kept the same control block.
After I finished the edits, I noticed that some other messages in the Problem SLC were erroring out. The error message was something like 'already at maximum connections', so I opened the CH1 diagnostics and found that there were 16 connections in use...that can't be right...
So, I did some online editing to temporarily halt all of the messages (four) between the two PLCs by deleting the rungs and then testing the edits. This did not make any difference...even after waiting for about 30 minutes...I still don't know what tells the SLC to begin releasing connections...There is still another SLC that I could not get to which was also still reading from it, but that should only be one connection.
So, I put the SLC in program mode and back to remote run using RSLogix...no difference. Then I uploaded and saved the program, went offline, and then went to the channel connections tab and pushed the clear button to zero out all the counts. I then downloaded the program and put it back in run mode. The connections jumped right back to 16.
Finally, to clear this up, I went to the SLC and cycled power. Now we are back to the normal 6-7 connections. Apparently the ethernet daughtercard holds onto connections even when the SLC is in program mode...which makes sense, cause it still needs to be able to talk to other stuff...
So, this is more informational for others, but I am still curious about the mechanism that would allow those extra connections to be created and then released. I am not 100% sure the editing of the message instructions had anything to do with it, since I did not look for any errors before I started making those edits, and the edits were done in the other PLC, and continued to work even while the connections were maxed out.
Thanks for any insight about how these mysterious connections actually work.
Paul
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