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Basic Terms - Consumer / Provider
In this application note, so-called provider or consumer are mentioned. In principle, the provider is the subscriberdevice who sends the payload, regardless of his role (controller or device). The consumer is thus the one who receives the data.
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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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Note that in case of a certification, the correct treatment of the status values may be necessary.
Bit 0:
| Value (hex) | Bedeutungmeaning |
|---|---|
| 0x0 | No IOxS octet follows |
| 0x1 | One more IOxS octet follows |
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Reserved
Bit 5 to 6:
| Value (hex) | Bedeutungmeaning |
|---|---|
| 0x0 | detects inside Subslot |
| 0x1 | detects inside Slot |
| 0x2 | detects inside IO-Device |
| 0x3 | detects inside IO-Controller |
Bit 7:
| Value (hex) | Bedeutungmeaning |
|---|---|
| 0x0 | Bad: The data field contains invalid data |
| 0x1 | Good: The data field contains valid data |
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Application environment
Selective handling
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 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 figure shows the entire structure of the process image in the IO monitor. All modules are released by the set "GOOD" (0x80) flag and are transmitted. Reading the process data from the process image requires knowledge of the position of the user data.
