Data Bus Interface Definition and Instantiation

Hi Everyone,
Having defined the functional and logical interfaces between my System of Interest and the interfacing systems, I am now trying to define the Exchange Item Elements.
My system interfaces with an external system via an ARINC 429 data bus. All messages on the data bus are constructed of the following parameters, each of which has some properties e.g. Least Significant Bit (LSB), Most Significant Bit (MSB) etc.:
I am expecting to be able to define this structure only once and then instantiate it as many times as required to define the complete set of messages (which thankfully is only 3 in this instance).
I have created a Capella Library element of the data bus structure (See “Data Bus Structure” attachment)
I have then incorporated it into my system model, defined the three messages as Exchange Items and related them through Exchange Item Elements (See “Data Bus Instantiation” attachment).
I have also related the Exchange Items to each of the associated Function Exchanges (See “Allocated Exchange Elements” attachment.
However, I don’t know how to instantiate the data bus properties for each message (Exchange Item). You may see in the “Data Bus Instantiation” attachment that I have used Literal Numeric Values to define the label properties, but I can’t find a way to associate them with associated Exchange Item.
Am I going about this the right way and just missing something or have I gone completely in the wrong directly?
Any advise would be greatly appreciated.

Data Bus Structure.JPG
Data Bus Instantiation.JPG
Allocated Exchange Elements.JPG
Data Bus Structure.JPG
Data Bus Instantiation.JPG
Allocated Exchange Elements.JPG

Hi Kevin,
perhaps constraint (where you can provide your class element as owned specification) added to every exchange item element (belonging to given exchange item) would work for you.


Hi Jakub,
Thanks for the response.
This could work for now and I will have to see how I get on before I can provide any more insightful feedback.
I’m still in the early stages of learning Capella and I’m still trying to figure out precisely what it is I’m trying to get out of it and so it is quite the iterative process.
Thanks again!

Just my 2 cents: you can define Data Values as well, and refer to them in the Owned Specification of the constraint. This way, if you have several constraints that refer to the same value, and this value changes, you will only need to change it in one place.


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