Hello,
It is hard to say without checking the project,but when you have such a problem for all absolute addresses

regarding , try to define a symbol for the global DB (DB40,41) and use the (syntax "DB name". name of cell) and see the result. Also ,check both DB if the "Optimized block access" is removed in their attributes.If  it is the case,try again with absolute addresses.

Final suggestion would be uploading your STEP 7 modbus library here for some tests.

I hope this helps,

Hamid Hosseini

Thank a lot Hamid,

I've   already checked that the DBs have not checked "optimized block access"  attribute.

You can see attached a sample program ( downloaded from siemens support  site ) that I am trying to use.

When I am open this project and compile FC10, FC21, FC23  there is the same problem.

I see the problem. I guess, TIA Portal can not process absolute address inside a DB without a symbol.It means, you will have problem for a full-qualified access of DB elements of a smaller size inside a whole (like access a bit in array of bytes).I don't know the reason, perhaps it is a limitation of software, but I can suggest the following workaround:

      OPN   "D_41"

      SET
      =     %DBX0.0              //RCV with EN_R=1

// ------------------------
// RCV with Instance-DB
// ------------------------
      A     %DBX0.0
      =     "IDB_P_RCV_RK".EN_R
      L     %DBW16
      T     "IDB_P_RCV_RK".LADDR

and the rest of block.For more information, please start a new support request.

Thank you very much,

It is helpful for me.

I think that  this sample program is not enough tested by Siemens befor publishing.

I  keep searching   for decision.

The problem is solved with upgrade TIA 13 to  SP1 Upd2.

Hi

thanks for the info, I too had the same prob it was due to accessing of address multiple time for eg. U have declared db5.dbd46 and if u try to access individual bit of that double word it shows the warning BT doest cause any impact on programme...