IODDTs are predefined by the manufacturer, and contain input/output language objects belonging to an application-specific module.
Modbus, Character Mode and Uni-Telway communications have five associated IODDTs:
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T_COM_STS_GEN: applies to communication protocols except Fipio and Ethernet
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T_COM_MB: specific to Modbus communication
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T_COM_CHAR: specific to Character Mode communication
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T_COM_UTW_M: specific to Uni-Telway master communication
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T_COM_UTW_S: specific to Uni-Telway slave 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 their correct operation.
There are two types of language objects:
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implicit exchange objects, which are automatically exchanged at each cycle of the task associated with the module,
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explicit exchange objects, which are exchanged when requested to do so by the application, using explicit exchange instructions.
The implicit exchanges concern module status, communication signals, slaves, etc.
The explicit exchanges are used to set the module and perform diagnostics.
