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M&M FDT 1.2.1 Online Specification |
Interfaces and Methods - Schemas - FDT Specification - Quicklinks - Abbreviations
4.5.1.2 IFdtChannel::GetChannelPath()
| This method can be called in the states: |       |
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HRESULT GetChannelPath ( [out, retval] FdtXPath result ); |
Description:
| Returns an identifier for a channel. |
Parameters:
Return Value:
| result | Path that identifies the channel within the device. |
Behavior:
| Returns the path that identifies the channel within the device. The string must not be empty. It always starts with the systemTag of the device instance followed by the channel id. The DTM has to guarantee that the path is unique for a device instance. The channel path is the base information to handle the system structure at IFdtTopology and IFdtChannelSubTopology. <systemTag>/<id> Furthermore the channelPath contains the information where to find the channel within the parameter document available via IDtmParameter::GetParameters() and so at least in case of a monolithic DTM the information whether the channel belongs to a device or module. In case of communication channels there are some special rules for building the channelPath. How to generate the channelPath of a communication channel, which also acts as a process channel for data that it receives from a process channel of a child device, depends on the functionality of the channel. If the channel is passive, that means that it receives its data from a child device and provides this data without any changes within its own channel-parameter document, the channelPath must be built out of system tag and channel id of the own device instance and the system tag of the child device and the id of the marshalled channel. <systemTag>/<id>//<systemTag>/<id> If the channel is active, that means that it receives its data from a child device for processing and provides the result within its own channel-parameter document, the channelPath must be built out of the system tag and channel id of the own device instance. <systemTag>/<id> This allows navigation through the internal channel assignment of a device with gateway functionality. In general if the channelPath of an channel has changed the according DTM has to send OnParameterChanged() with respect to the possible behavior of other FDT objects. |
Comments:
| An example for such a channel is a Profibus remote I/O that reads the primary variable (provided as HART channel) of an underlying HART device and provides this value within its own cyclic I/O data (Profibus DP Channel). |
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Last updated 2015-02-05 15:17
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