Profinet Multi Controller Access
Section 2 of the Profinet IO Configuration manual says that "In Multi Controller Access using 800xA, each controller in 800xA should be configured with only those modules to which the controller requires communication. Parallel access to the same submodule should not be done as it results in access violation errors during configuration."
In theory, Profinet allows Multiple controllers to access the same Devices and read data from them. (only one controller can write). So two controllers can read the same IO station.
Has anyone actually tried this to see if it works ?
What happens if two controllers try to read the same IO channel - do both controllers actually get the data ?
There are two functionalities in PROFINET describing the parallel access from different controllers to same device:
Shared Device: Different data go to different controller
The device is a modular one. It has several modules and submodules. Examples: Remote I/O with several I/O-modules or an electrical device like PNQ22 with up to 4 UMC100.
Shared device means, that each I/O-module of the Remote I/O can be accessed by a different controller. But only one controller can access the specific I/O-module. A second one will get an error indication "Locked by other controller/supervisor". The same is with PNQ22/UMC100. Assuming that shared device is supported yet then each UMC100 could be accessed by a different controller.
Note: support for shared device with PNQ22/UMC100 is planned functionality and will come with later release.
PROFINET Device in 800xA having support for shared device functionality is MNS iS with MLink. The MLink is able to provide data to 4 controller.
Shared Input: Same data go to different controller
Same as shared device but in addition different controllers can access same I/O-module for reading input data. But only one controller is able to write output data. This is a complex functionality and not supported by any vendor so far. Also in 800xA we do not have support for it yet and no support planned for it so far. If someone tries to configure same input module in different controllers also an error indication "Locked by other controller/supervisor" will show up.