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Old December 6th, 2021, 02:23 PM   #16
TheWaterboy
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Ken:
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Are you 100% for absolutely certain that data table file N7 is at least 40 elements in length, so the PLC-5 can respond with the values of N7:30-39 ? It seems it would have to be, because the reply highlighted in green has 10 words of data in it.
40 elements in length? Or 10? There are 100 elements in the N7 register.
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Old December 7th, 2021, 01:04 AM   #17
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If anyone was following along; TheWaterboy and I have taken the discussion offline because there are program files and network traffic that are confidential.

Also, because we don't know what the heck is going on.

There's something in the network that instead of replying to a DF1 Master poll with SRC = [address of itself] and DST = [address of the master] is replying with both values = [address of itself], which is something a DF1 Master doesn't expect and can't handle. That anomalous reply is being made to the same message that an ordinary PLC-5 is replying to correctly.


I feel like the TV ad in the original 1984 Ghostbusters: "If YOU have seen anomalous DF1 behavior, call us right away. WE BELIEVE YOU !"
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Old December 7th, 2021, 01:17 AM   #18
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I have been following with some interest, please do let us know what you find!

I don't have any KE modules or PLC5s, but funky poll / responses is something I've had to deal with for other protocols so it's always something I'm keen to hear about
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Old December 7th, 2021, 03:27 PM   #19
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Quote:
Originally Posted by Ken Roach View Post
I feel like the TV ad in the original 1984 Ghostbusters: "If YOU have seen anomalous DF1 behavior, call us right away. WE BELIEVE YOU !"

That would make me . . .

slimed.jpg

.
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Old December 8th, 2021, 06:59 PM   #20
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For those of you playing along at home...

The odd data was coming from a 1785-KE module on a different site 2 miles away. KE modules are supposed to be transparent but if you address them they will respond, though they are only capable of responding with the diagnostic registers.

DF1 half duplex is a broadcast format so when I polled that address for an N register every device with a radio could hear that request. Since the KE heard it, it could only reply saying I can't do that. But it WAS a proper reply and it was processed as such right along with the intended stations reply mangling the entire thing.

I found it by polling only that one address, then going into one remote radio at a time through ssh cli, turning off the com port for that location and seeing if replies stop. When they did I had my location.

After driving to the location, RSLinx showed me the addresses on the DH+ network and the KE was obviously the culprit. Changing the address of that KE module was all it took to exorsize the demon.

The reason this was never seen before was that old radio system (Esteem 192C) handled DF1 internally. It encapsulated and routed the traffic to ONLY the intended destination radio programmed into the master polling radio. Because of that the other sites never heard the broadcast so the module never had to respond. The new radios from GE (Orbit MCR) do not provide the ENI option like the SD radios did so they can't do anything but broadcast it.

BTW, The PLX51-ENI module does not handle this kind of error very well. TCP resets are not the proper thing to do. That sent me on wild goose chase.

Well that's over. Thanks Ken for all the help trying to decode what this thing was. If you ever work out a way to msg for ID, that might be helpful to anyone still dealing in the forgotten dark magic of DF1 over radio.

.
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Old December 9th, 2021, 05:37 PM   #21
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Thanks for the follow up! I was following along with interest and I'm glad I wasn't left hanging.

I swear that we could assemble a crack industrial-ghost-busters team with some of the PLCTalk members here and travel the world solving problems one site at a time.
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