/// <summary>
    /// 信息头
    /// </summary>
    [Serializable]
    [StructLayoutAttribute(LayoutKind.Sequential,CharSet.Ansi,Pack=1)]
    public struct MessageHead
    {
        /// <summary>
        /// 功能码枚举
        /// </summary>
        [System.Runtime.InteropServices.MarshalAs(UnmanagedType.U1,SizeConst=1)]
        public byte OperationCode;

        /// <summary>
        /// 数据类型
        /// </summary>
        [System.Runtime.InteropServices.MarshalAs(UnmanagedType.U1,SizeConst=1)]
        public byte DataType;

        /// <summary>
        /// 帧ID号
        /// </summary>
        [System.Runtime.InteropServices.MarshalAs(UnmanagedType.U2,SizeConst=2)]
        public ushort FrameID;

        /// <summary>
        /// 保留（存储返回结果）
        /// </summary>
        [System.Runtime.InteropServices.MarshalAs(UnmanagedType.U1,SizeConst=1)]
        public byte Retain;

        /// <summary>
        /// 数据长度
        /// </summary>
        [System.Runtime.InteropServices.MarshalAs(UnmanagedType.U4,SizeConst=4)]
        public uint DataLength;
         
    }