AUTOSAR and Time Synchronization over CAN

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If you are checking documentation from AUTOSAR about time synchronization over CAN you can get a bit confused by looking at figure 1. Here I’ll try to clear it out with some examples. 

 

Figure 1 - CAN Time Synchronization mechanism


If you put numbers inside equations you will get something like the result in figure 2. The result is 4.100 [s] but by looking at the graph you will expect to get 5.100 [s]. That is because this sync method doesn’t include compensation for transfer (latency) delay. Engineers who developed this method consider CAN communication delay is negligible, but they didn’t draw a sequence diagram that way.



Figure 2 - calculation example with delay problem


To make things more understandable let's draw a graph without communication delay. 

Figure 3 - calculation example with no delay problem


Does this have more sense now? 


Comments

  1. lehoang318January 8, 2022 at 6:38 AM

    Thank you for the clarification.
    I had the same concern regarding this specs.

    ReplyDelete
    Replies
    1. Igor MišićJanuary 8, 2022 at 12:20 PM

      Thank you for leaving a comment. I am glad this was useful.

      Delete

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