OSEK-COM

The OSEK COM layer’s model consists of three layers: the data link layer, the network layer and the interaction layer. The interaction layer is entirely specified by OSEK COM, but the data link layer and the network layer are not specified by OSEK COM. The interaction layer provides services for the transfer of message objects. The network layer handles the message segmentation of message frames coming from the upper layers and the message are sent as individual data frame to the data link layer. The data link layer provides to the upper layers services for the transfer of individual data frames from an ECU (Electronic Control Unit) to another ECU across a physical link like for example the CAN bus.

In case of internal communication, the transfer of the message is entirely handled by the interaction layer. The message object coming from the application layer is stored in a sending message object and then transferred to a receiving message object. For the external communication, the message object is copied in an I-PDU (Interaction Protocol Data Unit), before being transmitted to another ECU using the services provided by the underlying layers. An I-PDU is structured like a message object, but it contains an additional overhead with relevant information for the underlying layers. For the reception of the message object, the message coming from the underlying layers is stored in an I-PDU and then copied in a receiving message object.