(IEC 60870) what is the correct response when receiving invalid COT or CA or IOA values.

When a device receives an ASDU with an unknown COT or CA or IOA value what type of Information Object should be included in the response?
I know that the response COT could have one of these values :

COT=44
COT=45
COT=46
unknown type identification
unknown cause of transmission
unknown common address of ASDU
but what about the information objects? is it supposed to echo back the received Information Objects it received ?
 
COT=47 STAND for Unknow Informations object

To get informations objets :

i get that.
assuming that I'm the device,
i have to reply with an asdu with cot of 47. but i also have to include at least one information object in my asdu as the standard states. what information object would that be?
 
i get that.
assuming that I'm the device,
i have to reply with an asdu with cot of 47. but i also have to include at least one information object in my asdu as the standard states. what information object would that be?
Here is some notes from a manual that i got :
Will have a search on that question...

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Check these notes from a good doc ...:

I guess it really depend on the SQ (STRUCTURE QUALIFIER ) and mapping for sure

View attachment 1590
Thanks for the answer but:
SQ bit specifies how information objects are addressed in an ASDU but does not tell which information objects should be included in case an ASDU with invalid CA/COT/IOA arrives.
In this case we have to tell the controlling station that the request it sent is invalid (we do that by setting the COT value that says what is wrong). Since we can't send an empty ASDU back (an ASDU with no information objects) we have to include something (at least one information object) in it but I have no idea what that is.
 
Thanks for the answer but:
SQ bit specifies how information objects are addressed in an ASDU but does not tell which information objects should be included in case an ASDU with invalid CA/COT/IOA arrives.
In this case we have to tell the controlling station that the request it sent is invalid (we do that by setting the COT value that says what is wrong). Since we can't send an empty ASDU back (an ASDU with no information objects) we have to include something (at least one information object) in it but I have no idea what that is.
Okay so what is the meaning of " ASDU with invalid CA/COT/IOA arrives " the term invalid is not clear and can be misinterpreted...

Do you mean a "wrong value " for example on a voltage value...
 
Okay so what is the meaning of " ASDU with invalid CA/COT/IOA arrives " the term invalid is not clear and can be misinterpreted...

Do you mean a "wrong value " for example on a voltage value...
Let's say a station has the common address of 200 and a master sends an ASDU (interrogation/read etc...) to it that has the CA of 150.
this would mean that this ASDU is not meant for the station (it has an invalid/unknown value for the station) and the station should respond with a COT of 47
 
Okay got it

So have a read on the hereafter document it can help you ! it is talking of the third byte of IOA which is used to determine unambiguous addresses within specific system....

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