FOR loop_3 := 0 TO 7 DO
IF sequence[0] AND D20_LoCly_Hpos THEN
sequence_bit[0] := true;
ELSIF
NOT D20_LoCly_Hpos THEN
sequence_bit[0] := false;
END_IF;
IF sequence[loop_3 +1] AND sequence_bit[loop_3] AND D20_LoCly_Hpos THEN
sequence_bit[loop_3 +1] := true;
ELSIF
NOT D20_LoCly_Hpos THEN
sequence_bit[loop_3 +1] := false;
END_IF;
IF (sequence[loop_3 +1] AND sequence_bit[loop_3]) OR sequence[0] THEN
D20_Sequence_Act := true;
ELSE
D20_Sequence_Act := false;
END_IF;
END_FOR;
前面的IF语句正常，最后一个IF语句，只在【0】时为真，为什么啊？