Hey guys,

Let's say I have some logic which will return a value. Based on the outcome I would like to run a certain program/function block. The values of this logic can vary from say 0 to 100. For example value = 50, run Program 50.

I've searched the manual and found the ADRINST function, which in my case can come in pretty handy. But the documentation on this function is limited:

ADRINST

Adress function, not prescribed by the standard IEC61131-3.

ADRINST within a function block instance returns the address of the instance in a DWORD. This

address then can be sent to functions and be treated there as a pointer or it can be assigned to a

pointer within the project.

Is there a beter way to handle the problem discribed above, or is there a way to use the pointer returned by the ADRINST function and call a function?

Greeting,

RikeR

The direct call of function blocks e.g. via a string variable with the name of the FB can be realised by the means of some detours.

What you need in order to do so is the CAA_Callback.lib. This is an external library that provides the function CB_CallFunctionByIndex .

The call could e.g. look like this:

dwValue := CB_CallFunctionByIndex(INDEXOF(CallbackFBI1), dwParam1, dwParam2, dwParam3);

Please find the sepcification of the CAA_Callback.lib attached (unfortunately German only).
It is important that this function can only call another function that fulfils the following requests:

A possible prototype thus looks like this:

FUNCTION CallbackFBI1: DWORD
VAR_INPUT
   Param1: DWORD;
   Param2: DWORD;
   Param3: DWORD;
END_VAR

Please find a CoDeSys project with the name FB-Pointer-Liste.pro attached. There the following approach is considered:
If the CAA_Callback.lib is not available you could probably write your own c library. It should have something like this:

unsigned long CB_CallFunctionByIndex(
                              short sPOUIndex,
                              unsigned long ulParam1,
                              unsigned long ulParam2,
                              unsigned long ulParam3)
{
   void* pPlcFunctions;
   unsigned long ulValue = 0;
   if(sPOUIndex != -1)
   {
      pPlcFunctions = RtsGetIecFctPointer(sPOUIndex);
      if (RtsProgramLoaded() && pPlcFunctions != 0)
      {
         ulValue = SysCallWith3Param(
                     (PFCALLBACK)pPlcFunctions,
                     ulParam1,
                     ulParam2,
                     ulParam3
                  );
      }
   }
   return(ulValue);
}

CAA_Callback.pdf [45.66 KiB]

CAA_Callback.zip [3.92 KiB]

FB Pointer Liste.zip [5.4 KiB]

hi!

I have the similar question. I try to use System event EXCPT_WATCHDOG in Task configuration as follows:

1) watchdog in main program PLC_PRG is enabled and set to 30 sec;

2) main program represents endless loop

WHILE TRUE DO
;
END_WHILE

3) System event EXCPT_WATCHDOG is set, called POU have only one operator ```

SysResetPlcProgram(0);

``` from PLC control system library SysLibPlcCtrl.lib (I want to reset my program when watchdog triggered)

It seems to be right but doesn't work! Software watchdog of IEC-task never triggers and I can't reset my program at the same time hardware watchdog of ThinkIO always triggers and indicating PLC hang-up.

Please explain me how I should reset program or completely PLC?

Your callback must return 0. Just have a look to the attached program which is working for me with PlcWinNt

testwd.pro [25.96 KiB]