Using arrays in IEC PLC

Products: ACR9600,9630,9640

Note:

• uses 16bit integers to represent array subscripts for performance reasons. Arrays should not be declared in a way to use subscripts exceeding 16bit address limits, as this would lead to undefined behavior

• The upper and lower bounds must always be specified as integers in the declaration. It is not possible to assign/change array length using a variable at run-time. 

• Expression are not allowed in the [index] assignment of any array. For example, x2[MyIndex+1]:=10;  would result in an error. Instead, evaluate the expression prior to using in the index field:    MyIndex:=MyIndex+1; x2[MyIndex]:=10;

   

   

Example1

The following declares an array of five integers and assigns initial values:
VAR
x1: ARRAY[0..4] of INT := [1,2,3,4,5];
END_VAR

 

Example2

TYPE
UserData : STRUCT
 ID : UDINT;
 Score : REAL;
END_STRUCT;
END_TYPE

for index:=1 to 10 by 1 do
  (*resets the top ten back*)
  TopTen[index].id:=index;
  TopTen[index].score:=100000.0;
end_for;

for index:=1 to 100 by 1 do
 readparm.ParameterNumber:=39300+index;
 ReadParm( Enable:=true | val:=value);
 uID :=index;

 
 if val >0.1 then
  KeepChecking:=true;
  IsTopTen:=False;
  index2:=1;
  while KeepChecking and Index2<11 do
   if val<TopTen[index2].score then
    keepchecking:=false;
    IsTopTen:=true;
    tempData1.score:=val;
    tempData1.id:=uid;
   end_if;
   index2:=index2+1;
  end_while;
  if IsTopTen then
   index2:=index2-1;
   tempdata2:=TopTen[index2];
   TopTen[index2]:=tempdata1;
   index2:=index2+1;
   for index3:=index2 to 10 by 1 do
    tempdata1:=TopTen[index3];
    TopTen[index3]:=tempdata2;
    tempdata2:=tempdata1;
   end_for;
  end_if;
 end_if;
  
 
  
END_for;