FUNCTION_BLOCK "FB_GetSumOfArithmeticProgression"

TITLE = FB_GetArithmeticProgressionSum

{ S7_Optimized_Access := 'TRUE' }

VERSION : 0.1

//求公差为1的等差数列之和

   VAR_INPUT

      "begin" { ExternalAccessible := 'False'; ExternalVisible := 'False'; ExternalWritable := 'False'} : DInt;

      last { ExternalAccessible := 'False'; ExternalVisible := 'False'; ExternalWritable := 'False'} : DInt;

   END_VAR

   VAR_OUTPUT

      error : Bool;

      sum { ExternalAccessible := 'False'; ExternalVisible := 'False'; ExternalWritable := 'False'} : DInt;

   END_VAR

   VAR

      statOldBegin : DInt;

      statOldLast : DInt;

      statIndex : DInt;

      statError : Bool;

      statSum : DInt;

   END_VAR

   VAR_TEMP

      tempBegin : DInt;

      tempLast : DInt;

      tempIndex : DInt;

      tempSum : DInt;

   END_VAR

   VAR CONSTANT

      INCREMENT : DInt := 16#1;

      ZERO : DInt := 16#0;

   END_VAR

BEGIN

   REGION INITIALIZATION  

       #tempBegin := #begin;

       #tempLast := #last;

       #statOldBegin := #ZERO;

       #statOldLast := #ZERO;

       #statIndex := #ZERO;

       #statError := FALSE;

       #statSum := #ZERO;

   END_REGION

   REGION LOGIC & CONTROL

       #statError := #tempBegin > #tempLast;

       IF #statError = FALSE OR #tempBegin <> #statOldBegin OR #tempLast <> #statOldLast THEN    //no error and setpoint has changed,then calculate the sum

           IF #statIndex <> #tempLast THEN

               FOR #tempIndex := #tempBegin TO #tempLast BY #INCREMENT DO

                   #statSum := #statSum + #tempIndex;

                   #statIndex := #tempIndex;

               END_FOR;

           END_IF;

           #statOldBegin := #tempBegin;

           #statOldLast := #tempLast;

       END_IF;

   END_REGION

   REGION OUTPUTS

       #error := #statError;

       #sum := #statSum;

   END_REGION

END_FUNCTION_BLOCK