plchomer

Groo Thanks for your patience. You have helped me clear my thinking on this issue. My only question remaining is how can I find where FB35 is called so I can inspect the logic that feeds the input to the function. So you say i can cross reference FB35 to find it's call locations.  This I don't know yet how to do with my step 7. If you can give some guidance I would greatly appreciate it.   Thanks

Well at this point I don't know how to find the one call to FB35 that has DB77 as an instance so yes I only need to find the right call. I assumed I would have to look at all of them to find the right one.  I am a noob at this stuff, having to learn on the job.. It seems that any modification should be done in an output section of the instance block making finding the call point unnecessary. Thanks    

Greetings I have a nice new s7-400 program to modify and troubleshoot using step 7. Now my problem is this code if full of bits being used globally which do not show up in the cross reference as having been written anywhere. For instance DB77.DBX1.3  has no point where cross reference can find it is set. So I find the Function block where db77 is an instance.  Lets say FB35 In FB35  where DB77 is an instance I find that 1.3 is in the input section,  .. awesome eh? This code is full of this type of usage.  In the past I have found that the solution is where FB35 is called a logic input value at the call site is fed into a FB35 input and my mystery bit is being set that way. My two questions 1    I apparently need to be able to find every instance of a call to FB35 to track down the status of this bit.       and how can I do this in step 7.   2   Is this programming method considered as bad policy as the many four letter words floating about my cube.   Thanks