Very strange problem with S7 function monitoring

[Pandiani 0]

Hello, I have came accross to a very strange problem when monitoring functions in STEP7. Let's say there is function FC10 in the PLC program. This function is called a couple of times in the proram. It has input and output data. Inputs to this functions are input variables (binary contacts) I0.0 and I0.1 (example). When I open one of the function calles for monitoring/Debugging I see that these input variables (inside the function) are pulsing (going ON and OFF). Of course in the really I0.0 and I0.1 are not pulsating. I thought that at first that I need to use call up path to see what is going on. However, I wan't able to monitor this function using call uppath to see real states of the functions. What I did was the following: 1. Debug ->Operation and then set Test operation 2. Debug ->Call enviroment and then check Call up path 3. In the list I see FC10 and OB1, I check OB1 as well (FC10 is already checked). I save, go to OB1 in LAD editor right click and choose monitor. Again monitored state showing inputs to first call of FC10. I was unable to monitor inputs and outputs of FC10 in any other call. Is it possible to use call up path and monitor functions? If so, can you please exaplain me what I'm doing wrong? I have used call up path successfully with FBs, but not sure about FCs. Now back to the original problem. I have created VAT table and put all input variables to all FC calls (there are three FC10 calls). VAT shows that no input variables are pulsating. Also when monitoring in OB1 (where FC10s are called), there are no changes in input variables. But when I open FC10 for monitoring I see pulsating input variables. That is very strange and cannot explain this. Also, on PLC on input modues I see no changes on LEDs) Did anyone had similar experience? If I resolve the problem with monitoring function call that I want I'll be able to figure out what is happening inside the function. I must admit, that these pulsating variables lead me to wrong tranck when I tried to follow PLC program to determine what is happening in the process. Thank you for your help. Edited 30 May 2009 by Pandiani

[JesperMP 2]

Hi Pandiani. Monitor with Call-up path works the same way with FBs and FCs. Simply activate Test mode, and then select Monitor with call-up path when you select an FC block.

[Groo 7]

If all FC's are called from OB1 then selecting a path would not help, as they all use the same path. Edit: If you want to check one instance of a FC block which is difficult to do by path, copy the FC to a temp new block and re-program the OB to call the new block in that one instance that you want to monitor. Edited 31 May 2009 by Groo

[Peter Nachtwey 15]

It sounds like you are calling FC10 with the inputs bits begin on in some cases and off in other cases. There is no good solution except to make sure the other FC10s are not called. Another solution is to duplicate FC10 and make a FC11 and FC12 and substitute these functions for F10 in the difference places.

[JesperMP 2]

I just made a test, and Monitor with call-up path works as intended. One FC10 called twice. In one FC10 call the inputs change, in the other it does not. Monitoring the one with the non-changing inputs displays them non-changing. And vice-versa. The way you have described how you use Monitor with call-up path does not sound right. Simply activate Test operation. Maybe you have to save the block again (*). Right-click on the block in the calling block, and then select Called Block .. Monitor with Call-up path. It is not calld just "Monitor". The block will be displayed with the online status of just that call. *: Sometimes I have to, to have the option Monitor with call-up path displayed.

[Pandiani 0]

Jesper I have done exactly what you described but I simply don't have monitor with call up path in the system menu. I hvae that for FBs but not with FCs if they're called in the same OB. I have problem which Groo described. Pease, have a look at the attached picture. Test operation is selected via Debug -> Operation ->Test operation in LAD editor in OB1. I used same procedure for FBs and it worked. Is this because of the version? I have STP 7 v5.3+HF2 (REV. LEVEL v5.3.0.2) I don't know what would be the reason for this? I appreciate any advice. Thanks P.S. I didn't respond for a while because I found this post when searching different forums: http://www.plctalk.net/qanda/showpost.php?...amp;postcount=3 and because of that didn't get back to this thread. But now, I 'm confused because Jesper wrote it is actually possible. Edited 21 Jun 2009 by Pandiani

[JesperMP 2]

I have found it to be a bit finicky with that it requires you donwload the latest version of the FC, and maybe also the calling block. Even if there is appearantly no change in the program, try to download the blocks anyway, and see if the menu option appears. As you can see in the screenshot I posted, it should be possible.