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Modbus Extension Card
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Modbus Extension Card for Bithouse Integral controller provides 2 modbus buses per card.
When a card is installed in the Integral controller, two new serial devices will be added 
by the operating system. The serial devices can be referred by custom names that are determined by the slot
the card has been installed.
All `internal` Extension Cards will appear under ``/dev/slots/internal/``. 

.. note:: Here internal installation means that the card has been installed to one of the six slots available in 
    Integral controller


The predictable name will use following pattern:
    ``M[slot number]_RS485_[bus number]``

Example1:
 - Modbus Card has been installed in the first slot (Slot 1) and we want to use the `first` bus, 
   the device in ioPort ``device`` field would be ``/dev/slots/internal/M1_RS485_1``

Example2:
    - Modbus Card has been installed in the fourth slot (Slot 4) and we want to use the `second` bus, 
      the device in ioPort ``device`` field would be ``/dev/slots/internal/M4_RS485_2``

See :doc:`/actiweb9_core/bus_devices/ioPorts/ioPorts` for more information about ioPorts