Access to Simple and Complex Data Types
Provide complex slave data points for the master
I/O modules make their data available as individual variables. Some I/O modules* also make data available as an array/structure. Depending on where and how deep you are in the tree structure of the fieldbus configurator and where you click [Map], you can access either the individual variables, arrays or the entire I/O module for these I/O modules. This option is available if a fieldbus coupler is used as the head station, since it forwards data unchanged from the I/O modules via the bus and allows full access to the data structures of the I/O modules.
Controllers, on the other hand, have the task of first preprocessing data from the I/O modules and passing only on the result via the bus. Application variables (“Program variables”) are linked within the application to data from the I/O modules, and only then are they communicated via the bus. The configuration is therefore not created automatically.
In the following example, the complex I/O module 750-645 has been inserted after a coupler. Either the I/O module as a whole (1), an array (2) or the individual variable (3) can be made available to the master.
The data points of the I/O modules are accessed uniformly, regardless of whether the I/O modules are connected directly to the controller or are addressed remotely via Modbus.
When the data points are made available, program blocks and instances of prepared function blocks, via which the data exchange is implemented, are automatically generated. You can use these program blocks directly in your program without further adjustments.
* The provision of complete data structures is possible for those I/O modules whose associated function blocks offer an iPort for connections: 0750-0636, 0750-0642, 0750-0643, 0753-1630, 0753-1631, 0753-0646, 0753-0647, 0753-0649, 075x-0482, 075x-0484, 075x-0493, 075x-0494, 075x-0495, 75x-0632, 075x-0635, 075x-0640, 075x-0644, 075x-0645, 075x0650, 075x-0651, 075x-0652, 075x-0653, 075x-0655, 075x-0657, 075x-0658, 075x-0670, 075x-0671, 075x-0672, 075x-0673, 075x-0511, 075x-0633
Use of the IPort for complex data structures
For complex I/O modules*) that exchange data via arrays, instances of so-called IPorts are automatically created in the used function blocks. This interface can be accessed directly. Via the IPorts data is received at each Modbus cycle and further processed via Modbus in a uniform way.
The IPort is accessed as shown below:
Modbus . Slave name _tcp . Module-/Data point name . IPort;
| Determined by using the Modbus configurator |
| Depending on the designation in the project |
| Determined by the selected connection type to the slave (e.g. tcp, udp) |
| Depending on the designation in the project |
| Determined by the use of the IPort |
Example in Structured Text (ST):
Example as Function Block Diagram (FBD):
