S7300 400超麻烦。这是我的程序里对OpDwCmd的处理。要处理高低字节，要使用AT：

VAR_IN_OUT

    OP_dwCmd  {S7_m_c:='true'}        : DWORD :=0;       // control word wincc

END_VAR

VAR   

    OPdwCmdHMI : DWORD := 16#0;                           // Operator Commands in HMI format

    OPabyCmdHMI AT OPdwCmdHMI : ARRAY [0..3] OF BYTE;    // look at HMI command byte-wise

    OPdwCmdPLC : DWORD := 16#0;                           // Operator Commands in PLC format

    OPabyCmdPLC AT OPdwCmdPLC : ARRAY [0..3] OF BYTE;    // look at plc command byte-wise

    OPabCmdPLC AT OPdwCmdPLC : ARRAY [0..31] OF BOOL;    // look at plc command bit-wise

END_VAR

Begin

    OPdwCmdHMI := OP_dwCmd;

    OPabyCmdPLC[0] := OPabyCmdHMI[3];

    OPabyCmdPLC[1] := OPabyCmdHMI[2];

    OPabyCmdPLC[2] := OPabyCmdHMI[1];

    OPabyCmdPLC[3] := OPabyCmdHMI[0]; 

// MANUAL / AUTOMATIC Operation 使用实例

    IF (QREMOTE AND LIOP AND MAN_L AND  NOT AUT_L) OR OPabCmdPLC[16]  THEN 

        QMAN_AUT := FALSE;

    ELSIF (QREMOTE AND LIOP AND AUT_L AND NOT MAN_L) OR OPabCmdPLC[17]  THEN 

        QMAN_AUT := TRUE;

    END_IF;