# Source code for pymodbus.constants

    '''
    Constants For Modbus Server/Client
    ----------------------------------

    This is the single location for storing default
    values for the servers and clients.
    '''
    from pymodbus.interfaces import Singleton

    class Defaults(Singleton):
        ''' A collection of modbus default values

        .. attribute:: Port

           The default modbus tcp server port (502)

        .. attribute:: Retries

           The default number of times a client should retry the given
           request before failing (3)

        .. attribute:: RetryOnEmpty

           A flag indicating if a transaction should be retried in the
           case that an empty response is received. This is useful for
           slow clients that may need more time to process a requst.

        .. attribute:: Timeout

           The default amount of time a client should wait for a request
           to be processed (3 seconds)

        .. attribute:: Reconnects

           The default number of times a client should attempt to reconnect
           before deciding the server is down (0)

        .. attribute:: TransactionId

           The starting transaction identifier number (0)

        .. attribute:: ProtocolId

           The modbus protocol id.  Currently this is set to 0 in all
           but proprietary implementations.

        .. attribute:: UnitId

           The modbus slave addrss.  Currently this is set to 0x00 which
           means this request should be broadcast to all the slave devices
           (really means that all the devices should respons).

        .. attribute:: Baudrate

           The speed at which the data is transmitted over the serial line.
           This defaults to 19200.

        .. attribute:: Parity

           The type of checksum to use to verify data integrity. This can be
           on of the following::

             - (E)ven - 1 0 1 0 | P(0)
             - (O)dd  - 1 0 1 0 | P(1)
             - (N)one - 1 0 1 0 | no parity

           This defaults to (N)one.

        .. attribute:: Bytesize

           The number of bits in a byte of serial data.  This can be one of
           5, 6, 7, or 8. This defaults to 8.

        .. attribute:: Stopbits

           The number of bits sent after each character in a message to
           indicate the end of the byte.  This defaults to 1.

        .. attribute:: ZeroMode

           Indicates if the slave datastore should use indexing at 0 or 1.
           More about this can be read in section 4.4 of the modbus specification.

        .. attribute:: IgnoreMissingSlaves

           In case a request is made to a missing slave, this defines if an error
           should be returned or simply ignored. This is useful for the case of a
           serial server emulater where a request to a non-existant slave on a bus
           will never respond. The client in this case will simply timeout.
        '''
        Port                = 502
        Retries             = 3
        RetryOnEmpty        = False
        Timeout             = 3
        Reconnects          = 0
        TransactionId       = 0
        ProtocolId          = 0
        UnitId              = 0x00
        Baudrate            = 19200
        Parity              = 'N'
        Bytesize            = 8
        Stopbits            = 1
        ZeroMode            = False
        IgnoreMissingSlaves = False

    class ModbusStatus(Singleton):
        '''
        These represent various status codes in the modbus
        protocol.

        .. attribute:: Waiting

           This indicates that a modbus device is currently
           waiting for a given request to finish some running task.

        .. attribute:: Ready

           This indicates that a modbus device is currently
           free to perform the next request task.

        .. attribute:: On

           This indicates that the given modbus entity is on

        .. attribute:: Off

           This indicates that the given modbus entity is off

        .. attribute:: SlaveOn

           This indicates that the given modbus slave is running

        .. attribute:: SlaveOff

           This indicates that the given modbus slave is not running
        '''
        Waiting  = 0xffff
        Ready    = 0x0000
        On       = 0xff00
        Off      = 0x0000
        SlaveOn  = 0xff
        SlaveOff = 0x00

    class Endian(Singleton):
        ''' An enumeration representing the various byte endianess.

        .. attribute:: Auto

           This indicates that the byte order is chosen by the
           current native environment.

        .. attribute:: Big

           This indicates that the bytes are in little endian format

        .. attribute:: Little

           This indicates that the bytes are in big endian format

        .. note:: I am simply borrowing the format strings from the
           python struct module for my convenience.
        '''
        Auto   = '@'
        Big    = '>'
        Little = '<'

    class ModbusPlusOperation(Singleton):
        ''' Represents the type of modbus plus request

        .. attribute:: GetStatistics

           Operation requesting that the current modbus plus statistics
           be returned in the response.

        .. attribute:: ClearStatistics

           Operation requesting that the current modbus plus statistics
           be cleared and not returned in the response.
        '''
        GetStatistics   = 0x0003
        ClearStatistics = 0x0004

    class DeviceInformation(Singleton):
        ''' Represents what type of device information to read

        .. attribute:: Basic

           This is the basic (required) device information to be returned.
           This includes VendorName, ProductCode, and MajorMinorRevision
           code.

        .. attribute:: Regular

           In addition to basic data objects, the device provides additional
           and optinoal identification and description data objects. All of
           the objects of this category are defined in the standard but their
           implementation is optional.

        .. attribute:: Extended

           In addition to regular data objects, the device provides additional
           and optional identification and description private data about the
           physical device itself. All of these data are device dependent.

        .. attribute:: Specific

           Request to return a single data object.
        '''
        Basic    = 0x01
        Regular  = 0x02
        Extended = 0x03
        Specific = 0x04

    class MoreData(Singleton):
        ''' Represents the more follows condition

        .. attribute:: Nothing

           This indiates that no more objects are going to be returned.

        .. attribute:: KeepReading

           This indicates that there are more objects to be returned.
        '''
        Nothing     = 0x00
        KeepReading = 0xFF

    #---------------------------------------------------------------------------#
    # Exported Identifiers
    #---------------------------------------------------------------------------#
    __all__ = [
        "Defaults", "ModbusStatus", "Endian",
        "ModbusPlusOperation",
        "DeviceInformation", "MoreData",
    ]