Autosar architecture basics, RTE & ECU COMMUNICATION

1. AUTOSAR
LAYEREDARCHITECTURE, RTE &
ECU COMMUNICATION
Omkar Rane 2005203 Powertrain Track

2. Content
 Autosar Layered Architecture.
 Virtual Function Bus and Run Time Environment.
 Virtual Function Bus Vs RTE.
 ECU Communication.

3. Autosar Layered Architecture
What is layered architecture ?
An architecture in which data moves from one defined level of processing to another.
E.g. Communication protocols use ISO OSI(Open Systems Interconnection) 7 layer model in computer network. Autosar
ECU software is abstracted and sub divided into basic software, runtime environment and application layer.

6. Virtual Function Bus & Autosar RTE layer
 ASW layer consist of SWC’s. RTE implements virtual function Bus Through which swc’s communicate with each other
and also with BSW modules.
 The communication can be possible in between SWC’s of same ECU as well as SWCs of other ECUs in a system.
 To achieve this functionality ,Virtual Function Bus or VFB , it is implemented in RTE layer of AUTOSAR.
 Its called “virtual” because there is no physical connection between SWCs, instead the SWCs of a ECU communicate
with SWCs of other ECUs in a system(vehicle) using low level communication bus like CAN or FlexRay.
 Because of this SWC is independent of actual underlying hardware and hence relocate ability of SWCs is possible i.e.
the same SWCs can be used on any ECU with any hardware platform.

7. VFB provides mechanisms for following services which are used by SWCs :
 Communication to other SWCs in the system.
 Communication with Sensors or actuators in the system.
 Providing access to standard services such as reading/ writing to memory.
 Responding to mode changes.
 Communication with external calibration and measurement instruments.
 Each ECU has customized RTE layer which implements the VFB for its respective SWCs.

9. Virtual Function Bus Vs Autosar RTE layer

10. ECU Communication
 Communication is between different SWC’s and ECU’s.
 Intra-ECU communication is realized virtually by defined function calls in RTE.
 Inter-ECU communication is realized by using the underlying communication bus like CAN or FlexRay
through COM Stack along with RTE.
 Communication between the SWC’s can be done either by sender-receiver or client server communication.

11. Sender-Receiver Communication
1.Queued S/R communication:
If the sender-receiver communication is configured as queued, then the sent data is processed
using a first-in-first-out (FIFO) queue with a specified length.
2.Non-queued S/R communication:
If the sender-receiver communication is configured as non-queued, then the receiver always has
access to the last sent data.

12. Queued S/R communicationNon-queued S/R communication

13. Implicit Communication- Implicit which means the runnable entity works on a local copy of an inter runnable variable.
A copy of read inter runnable variables is created on entry of the runnable. Changes are written back when the
runnable entity completes. This avoids concurrent access to inter runnable variables during runnable entity execution.
Explicit Communication- Explicit which means the runnable entity can directly access an inter runnable variable. Changes
are immediately visible to other runnable entities with explicit access to the inter runnable variable.

14. Client-Server Communication
 Client-server communication can be realized by synchronous communication (blocked) or asynchronous
communication(non-blocked).
 The client initiates the communication and requests a service from the server
 The client could be locked while it is waiting for an answer from the server
 The Client/server roles are defined by who is initiating the communication and could be switched
 A SWC can at the same time act as both client and server in different communications

15. Communication between Software Components mapped to different ECUs and is therefore concurrent and
involves potentially unreliable communication.
The communication mechanisms for the RTE are provided by the Communication Stack.
Inter ECU Communication via RTE & BSW
• Communication of Software components across ECUs in the network
• RTE will invoke AUTOSAR COM to transmit/receive signals
Inter ECU Communication

16. Communication between Software Components mapped to the same ECU.
Intra ECU Communication via RTE
•Communication among AUTOSAR Software components in the same ECU
•Communication between AUTOSAR Software component and BSW module
Intra ECU Communication

17. Communication between Software Components mapped to different partitions of the same ECU. It involves a context
switch and crossing a protection boundary (memory protection, timing protection, isolation on a core).
The communication mechanisms for the RTE are provided by the IOC. Inter-Core communication is used for multi-core
architectures and is similar to Inter-Partition communication.
Inter Partition Communication via RTE and IOC
•Communication between SWCs present in different partitions of the same core of the same ECU
• Communication between SWCs present in different cores of the same ECU
• RTE will use IOC (Inter O.S-Application Communication)
Inter-Partition ECU Communication

18. References
[1] Introduction to Autosar Lectures By Prof. Venkatesh Mane, available on YouTube
[2] Autosar official documentation, https://www.autosar.org/
[3] AUTOSAR Runtime Environment and Virtual Function Bus By Nico Naumann ,Department for
System Analysis and Modeling Hasso-Plattner Institute for IT-Systems Engineering ,Prof.-Dr.-
Helmert-Str. 2-3, D-14482 Potsdam
[4] AUTOSAR Handbook KPIT Technologies Ltd.
[5] https://automotivetechis.wordpress.com/autosar-concepts/
[6] https://autosartutorials.com/autosar-basics/
[7] https://www.rfwireless-world.com/Tutorials/AUTOSAR-tutorial.html
[8] https://sandeeptiwari.com/basics-of-autosar/
[9] https://www.embitel.com/product-engineering-2/automotive/autosar/
[10] https://www.einfochips.com/blog/autosar-in-automotive-industry/