OnlineMonitorSystem/NModbus/SlaveExceptionCodes.cs

namespace NModbus
{
    /// <summary>
    ///  Modbus slave exception codes
    /// </summary>
    public static class SlaveExceptionCodes
    {
        /// <summary>
        /// The function code received in the query is not an allowable action for the slave.  This may be because the function code is only applicable to newer devices, and was not implemented in the unit selected.  It could also indicate that the slave is in the wrong state to process a request of this type, for example because it is unconfigured and is being asked to return register values. If a Poll Program Complete command was issued, this code indicates that no program function preceded it.
        /// </summary>
        public const byte IllegalFunction = 1;

        /// <summary>
        /// The data address received in the query is not an allowable address for the slave. More specifically, the combination of reference number and transfer length is invalid. For a controller with 100 registers, a request with offset 96 and length 4 would succeed, a request with offset 96 and length 5 will generate exception 02.
        /// </summary>
        public const byte IllegalDataAddress = 2;

        /// <summary>
        /// A value contained in the query data field is not an allowable value for the slave.  This indicates a fault in the structure of remainder of a complex request, such as that the implied length is incorrect. It specifically does NOT mean that a data item submitted for storage in a register has a value outside the expectation of the application program, since the MODBUS protocol is unaware of the significance of any particular value of any particular register.
        /// </summary>
        public const byte IllegalDataValue = 3;

        /// <summary>
        /// An unrecoverable error occurred while the slave was attempting to perform the requested action.
        /// </summary>
        public const byte SlaveDeviceFailure = 4;

        /// <summary>
        /// Specialized use in conjunction with programming commands.
        /// 
        /// The slave has accepted the request and is processing it, but a long duration of time will be required to do so.T
        /// his response is returned to prevent a timeout error from occurring in the master.The master can next issue a 
        /// Poll Program Complete message to determine if processing is completed.
        /// </summary>
        public const byte Acknowledge = 5;

        /// <summary>
        /// Specialized use in conjunction with programming commands.
        /// The slave is engaged in processing a long-duration program command.The master should retransmit 
        /// the message later when the slave is free.
        /// </summary>
        public const byte SlaveDeviceBusy = 6;
    }
}