Overlap Detection Unit for CAN Bus Physical Layer Arbitration
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Solution Overview
Problem
The existing CAN bus systems face limitations in data transfer rates due to the slow arbitration phase, which hampers the overall data transfer speed and compatibility with newer CAN protocol specifications, necessitating a solution for coexistence and increased transfer rates while maintaining secure data transmission.
Innovation Solution
An overlap detection unit is introduced for user stations in the CAN bus system, capable of detecting bus state overlaps between different physical layers, allowing for seamless communication and error handling between CAN FD and CAN NG protocols without the need for gateways, by generating signals that indicate overlaps and enabling quick interference elimination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a second physical layer with higher bit rate is used for data transfer, then data transfer rate is improved, but compatibility with existing CAN protocol specifications deteriorates
Solution Approach 1:
The communication protocol is segmented into two distinct physical layers: a first physical layer compliant with existing CAN FD specifications and a second physical layer enabling higher bit rates. This segmentation allows different segments of the system to operate at different speeds, with the overlap detection unit managing the transition between layers, thereby achieving high-speed data transfer while maintaining compatibility with legacy devices.
2Adaptability or versatility
If user stations operate with different physical layers, then data transfer flexibility is improved, but detection of bus state overlaps becomes more difficult
Solution Approach 1:
The overlap detection unit serves as an intermediary component that monitors and detects bus state overlaps between the first and second physical layers. It specifically detects when a dominant bus state from the first physical layer conflicts with a recessive bus state from the second physical layer, enabling reliable communication despite the use of different physical layers by different user stations.
3Reliability
If arbitration is performed according to ISO 11898-1:2015 standard, then data transmission security is improved, but overall data transfer speed deteriorates
Solution Approach 1:
The system performs preliminary arbitration using the first physical layer according to the ISO 11898-1:2015 standard to establish secure and conflict-free bus access. Once arbitration is complete and the transmitting user station is determined, the system switches to the second physical layer for actual data transfer, thereby combining the security benefits of standard arbitration with the speed benefits of higher bit rate transmission.
Data Source
AI summary
An overlap detection unit for a user station of a serial bus system. The overlap detection unit includes a collision detection block for detecting bus states on a bus of the bus system, in which, in order to transmit a message, bus states of user stations of the bus system are generated on the bus with a first physical layer in a first communication phase, and are generated with a second physical layer in a second communication phase, the second physical layer being different from the first physical layer. The collision detection block generates a signal whose value indicates whether or not the bus states in the second communication phase have a level that corresponds to an overlap of the first and second physical layers or an overlap of two second physical layers, and the collision detection block is designed to output the signal for the user station.