Subscriber Station Pause Control for Deterministic Serial Bus Access
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Solution Overview
Problem
Existing bus systems in vehicles face challenges in achieving deterministic bus access and maximum bus utilization while supporting different communication standards and bit rates, particularly for applications with hard real-time requirements, such as autonomous vehicles.
Innovation Solution
A subscriber station with a communication control device and a pause module that manages communication phases with variable bit times and evaluates status information to generate transmission delay signals, ensuring deterministic access and high data rates even at maximum bus utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If CAN FD or CAN XL is used with higher bit rates in the data phase, then data transmission rate is improved, but deterministic bus access and worst-case delay guarantees deteriorate
Solution Approach 1:
The communication frame is segmented into arbitration phase and data phase with different bit rates. The arbitration phase uses lower bit rate (500 kbit/s) to ensure deterministic access and collision resolution, while the data phase uses higher bit rate (2-20 Mbit/s) for fast data transmission. This segmentation allows both deterministic control and high-speed data transfer.
Solution Approach 2:
The arbitration phase performs preliminary actions (collision resolution, priority determination) before the data phase begins. By resolving all access conflicts and determining transmission rights in advance at the lower bit rate, the system guarantees deterministic worst-case delays before high-speed data transmission starts.
2Reliability
If Ethernet PLCA method is used for deterministic bus access, then deterministic communication is improved, but device complexity and configuration complexity increase due to master node requirement and node number assignment
Solution Approach 1:
Each subscriber station autonomously determines its transmission timing based on frame counters and bit rate information embedded in the received signal. Nodes self-configure their transmission schedules without requiring manual node number assignment or a central master node, simplifying system configuration while maintaining determinism.
Solution Approach 2:
The system uses feedback from received frames (frame counters, bit rate indicators) to automatically adjust transmission timing. Each node monitors the bus, counts frames, and calculates its transmission delay based on feedback information from other nodes, enabling distributed deterministic scheduling without complex central control.
3Productivity
If bus utilization is increased to maximize data rate, then productivity is improved, but deterministic access and worst-case delay guarantees worsen
Solution Approach 1:
The system dynamically adjusts transmission parameters (bit rate, frame timing) based on real-time bus conditions and frame priorities. The arbitration phase dynamically resolves conflicts, and the data phase adapts bit rates to maximize utilization while the pause module ensures deterministic timing by pausing transmission when necessary to meet worst-case delay requirements.
Data Source
AI summary
A subscriber station and a method for deterministic communication in a serial bus system. The subscriber station has a communication control device for controlling a communication of the subscriber station by generating messages based on a frame and transmitting the messages to a bus of the bus system, and by evaluating at least one signal received from a bus of the bus system based on the frame, and a pause module for evaluating at least one item of status information output by the communication control device in relation to whether or not a predetermined frame has been received from the bus. The pause module is designed to generate and output a transmission delay signal based on a result of its evaluation, in order to delay or not delay the provision of a transmission message to the communication control device.