Pointer in Step 7

Ali-mohammadi · Feb 17, 2010

Hello everybody
How we can use pointer for Timers and counters,so that we could change Timer or counter address in the program?

L D[AR2P#0.0] · Feb 17, 2010

Source code example below:

Code:

FUNCTION FC 4 : VOID
TITLE =
VERSION : 0.1


VAR_INPUT
  iCounterNumber : INT ;    
  bCount : BOOL ;    
END_VAR
VAR_TEMP
  iCounterAddress : INT ;    
END_VAR
BEGIN
NETWORK
TITLE =

      L     #iCounterNumber; 
      T     #iCounterAddress; 
      A     #bCount; 
      CU    C [#iCounterAddress]; 


END_FUNCTION

Ali-mohammadi · Feb 21, 2010

Hello
Thanks for your answer.

Ali-mohammadi · Feb 21, 2010

Hello again
Is there any reason that u have defined POINTER as a TEMPORARY variable?

TurpoUrpo · Feb 21, 2010

in this instruction:

Code:

CU    C [#iCounterAddress];

#iCounterAddress have to be temp variable.

Ali-mohammadi · Feb 23, 2010

Hello TurpoUrpo

That is right,but I asked,why this pointer ought to be a temp variable?

TurpoUrpo · Feb 23, 2010

Values are passed on functions by pointer, not by copying the value. So it needs to be loaded from memory location and saved on temporary variable as value, to avoid double pointer.

L D[AR2P#0.0] · Feb 23, 2010

The pointer can be a temp variable, MW or DBW
Parameters, FB STAT variables, IW, PIW's are not permitted:

Pointer in Step 7

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