ISaGRAF. Version 3.4

         

è óñëîâèå ðàâíî FALSE, òî


Ñèíòàêñèñ:                 IF <boolean_expression> THEN

                                         <statement> ;

                                         <statement> ;

                                         ...

                                      ELSIF <boolean_expression> THEN

                                         <statement> ;

                                         <statement> ;

                                         ...

                                      ELSE

                                         <statement> ;

                                         <statement> ;

                                         ...

                                      END_IF;

Îïåðàòîðû ELSE è ELSIF - äîïîëíèòåëüíûå. Åñëè ELSE îïóùåí è óñëîâèå ðàâíî FALSE, òî íèêàêèõ èíñòðóêöèé íå âûïîëíÿåòñÿ.

Ïðèìåð:

(*ST ïðîãðàììà , èñïîëüçóþùàÿ îïåðàòîð IF*)

IF manual AND not (alarm) THEN

             level := manual_level;

             bx126 := bi12 OR bi45;

ELSIF over_mode THEN

             level := max_level;

ELSE

             level := (lv16 * 100) / scale;

END_IF;

(* IF ñòðóêòóðà  áåç ELSE *)

If overflow THEN

alarm_level := true;

END_IF;

        Îïåðàòîð CASE


Èìÿ:                              CASE... OF... ELSE...  END_CASE

Çíà÷åíèå:                   âûïîëíÿåò îäèí èëè íåñêîëüêî ñïèñêîâ ST îïåðàòîðîâ, âûáîð îñóùåñòâëÿåòñÿ â ñîîòâåòñòâèè ñ öåëûì âûðàæåíèåì

                                     

Ñèíòàêñèñ:                 CASE <integer_expression> OF

                                         <value> : <statements> ;

                                         <value> , <value> : <statements> ;

                                         ...

                                      ELSE

                                         <statements> ;

                                      END_CASE;

Çíà÷åíèåì CASE äîëæíà áûòü öåëàÿ êîíñòàíòà. Íåñêîëüêî çíà÷åíèé ðàçäåëåííûõ çàïÿòûìè ìîãóò óêàçûâàòü íà îäèí è òîò æå ñïèñîê îïåðàòîðîâ.

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