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Each configured module / submodule is assigned a provider and a consumer flag. It is exchanged between the participants via the process image together with the process data. A provider status is always sent in the same send direction as the process data, so it is located in the output image of the DPM and is hung behind the process data of the module. The consumer status is thus sent in the opposite direction to the user data, can therefore be found in the input image of the DPM and is placed above the process data of the next process data block.
The following figure shows the process data images for the input and output data of a sample configuration, respectively. With the aid of the module names or the slot indices <Slot_1 ... Slot_n> contained therein, the affiliation of the respective status flags can be determined. The address contained in the list shows with which offset the respective value can be reached on the process image.
The first four status bytes belong to the Device Access Point (DAP) and are integrated into the process image for each bus user. They have the data length of "0". Setting the flags to "GOOD" is mandatory for a successful communication setup.
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The respective modules, consisting of the process data block and the status flags, can be considered as one unit. Each unit can be traded selectively. The setting of the status flags thus has a specific effect on the respective module. The release of the process data of a module thus also requires the setting of certain status flags. This is also to be considered at the initial start of the bus communication:
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The following example shows the release of the last output module.
IO Monitor
The following figure shows the entire structure of the process image in the IO monitor. All modules are released by the set "GOOD" flag and are transmitted. Reading the process data from the process image requires knowledge of the position of the user data.
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