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Grundlagen FlexRay BasicsV 1.1 37
2.13 Protocol Data Unit
Protocol Data Units (PDU) are bus-independent data units, consisting of protocol data and
payload, which are processed by the layers of the protocol stack A PDU can consist of a
single signal or multiple signals. It has its own timing, and is able to show if its data is valid
by using an update-bit.
Figure 2.33 Overview of PDUs [VeSc11]
In AUTOSAR, there are different PDUs for each OSI-Layer (see Figure 2.33):
• I-PDU – Interaction Layer PDU, can consist of one or more signals, has its own
Update Bit.
• N-PDU – Network Layer PDU (optional)
• L-PDU – Data Link Layer PDU are the equivalent to Frames. They can contain one or
more I-PDU. It is possible to split up a single I-PDU between multiple L-PDU
Since FIBEX Version 3.0 I-PDUs are supported, but there is no definition for N- und L-
PDUs.
Using PDUs offers a lot of advantages. The receiver only has to process the data, if the
corresponding Update-Bit is set. Since otherwise the data has not been refreshed yet, or is
invalid. This saves processing power. It is also possible to have an easier structure for data.
Also, the data is directly provided, and it isn’t necessary to search for it in the frame.
Bäurle 12.10.2012