Bit that doesn't go anywhere

[PLC]

Dammit Jim.. I'm a doctor ... Not an engineer ....

 

[Wilso]

Is there anything other than the HMI that could be writing bits? Like a servo controller IO card? Or some other IO card in the rack that the PLC program itself doesn't refer to, just reads the bits & words written by it?

No servo controllers.

 

[Aabeck]

Another thought - maybe the PLC is writing a word that this bit is part of, and then later only checking this bit of the word.

 

[Wilso]

Another thought - maybe the PLC is writing a word that this bit is part of, and then later only checking this bit of the word.

I did consider something like that. But I can't find any reference to any byte, word, double word etc in that range.

 

[Aabeck]

Could you .zip & post the program & let us go through it?

 

[Wilso]

Too big.

 

[DwSoFt]

Would be helpful what brand and model of plc this
is etc. Also if it is critical to know aka giving you production grief maybe having someone with more experience remoting into it would help...

 

[Aabeck]

Another thought - could there be a bit shift command that is including the word M403 in it - (could be much lower & include quite a few words depending on the length of your machine.)

Another thought - did you do a search for the word M403 or double-word M402 & see if it pops up anywhere in the program?

 

[ggc]

Any chance there's a PC or a weld controller with a profibus or profinet card in this machine? Still wouldn't explain why it's turning on unexpectantly, but it could be the source of your state change.

 

[Aabeck]

Any chance there's a PC or a weld controller with a profibus or profinet card in this machine?

Or a remote PLC or HMI/PLC combination somewhere in one of the station cabinets? One of the systems I work on has 7 remote PLC's in cabinets and 5 HMI/PLC's at various stations separate from the main PLC & PC based HMI.

 

[rdrast]

If this is part of a sequencer, even an HMI could be controlling it.
There isn't nearly enough information here to make more than a guess as to what is happening.

 

[Manglemender]

It sound like it could be indirectly addresses as you can find no access to overlapping memory areas.

Nick

 

[Badger]

Is it linked to a shift register that moves on to "JOB 20".

 

[L D[AR2P#0.0]]

Too big.

Create a library with an S7 program in it, copy your blocks to the library and then archive/post the library.

 

[Jeebs]

L P#403.4
T LD20
A I0.0
= M [LD20]

Good luck finding that in the x-ref.