The IODDTs are predefined by the manufacturer. They contain input/output language objects belonging to the channel of an application-specific module.
Modbus and Character Mode communications have three associated IODDTs:
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T_COM_STS_GEN, which applies to communication protocols except Fipio and Ethernet.
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T_COM_MB_BMX, which is specific to Modbus communication.
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T_COM_CHAR_BMX, which is specific to Character Mode communication.
NOTE: IODDT variables can be created in two different ways:
Types of Language Objects
In each IODDT we find a set of language objects that enable us to control them and check that they are operating correctly.
There are two types of language objects:
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Implicit Exchange Objects: These objects are automatically exchanged on each cycle revolution of the associated with the processor.
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Explicit Exchange Objects: These objects are exchanged on the application's request, using explicit exchange instructions.
Implicit exchanges concern the status of the processors, communication signals, slaves, etc.
Explicit exchanges are used to define the processor settings and perform diagnostics.
