Subscriber Station Edge Counting for Bus Conflict Detection
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Solution Overview
Problem
Current serial bus systems, such as CAN and CAN FD, face limitations in data rate and user data capacity, particularly in vehicles where increasing functionality demands higher bandwidth and error robustness, while maintaining compatibility with existing arbitration mechanisms.
Innovation Solution
A device for a subscriber station in a serial bus system that includes a transmission signal analysis module, a reception signal analysis module, and an evaluation module to detect transmission conflicts by comparing edge counts, allowing for flexible operation and high error robustness, even at higher bit rates, without direct comparison of transmission and reception signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If higher clock frequencies are used to increase data rate beyond 1 Mbps, then data transmission speed is improved, but signal propagation time becomes significantly longer than bit time, making transmission conflict detection difficult
Solution Approach 1:
The patent introduces an intermediary mechanism (edge counting and difference evaluation) to indirectly detect transmission conflicts. Instead of directly comparing TxD and RxD signals which becomes unreliable at high speeds, the system counts edges of both signals and evaluates the difference, using this intermediate metric to detect conflicts even when propagation delay exceeds bit time.
Solution Approach 2:
The patent replaces the direct signal comparison mechanism (analog/electrical comparison) with a digital counting and evaluation mechanism. By substituting the direct signal path comparison with edge counting and mathematical evaluation of differences, the system achieves reliable conflict detection at high data rates where direct comparison fails.
2Device complexity
If direct comparison of TxD and RxD signals is used for conflict detection, then implementation is simple, but it becomes unreliable when signal propagation time is greater than bit time
Solution Approach 1:
The patent replaces the direct signal comparison mechanism (analog/electrical comparison) with a digital counting and evaluation mechanism. By substituting the direct signal path comparison with edge counting and mathematical evaluation of differences, the system achieves reliable conflict detection at high data rates where direct comparison fails.
Solution Approach 2:
The patent introduces an intermediary mechanism (edge counting and difference evaluation) to indirectly detect transmission conflicts. Instead of directly comparing TxD and RxD signals which becomes unreliable at high speeds, the system counts edges of both signals and evaluates the difference, using this intermediate metric to detect conflicts even when propagation delay exceeds bit time.
3Quantity of substance
If CAN FD message format is used to extend payload length to 64 bytes, then data capacity is improved, but it remains insufficient for applications requiring larger data transmission
Solution Approach 1:
The patent implements dynamic payload length adaptation by introducing a Payload Length Extension field that can dynamically indicate whether the payload is 64 bytes (CAN FD) or 4096 bytes (CAN XL). This dynamic mechanism allows the system to adapt to different data capacity requirements without being constrained to a fixed payload size, enabling versatility across different application scenarios.
Solution Approach 2:
The patent changes the payload length parameter from fixed values (8 or 64 bytes) to a dynamic parameter that can be 64 or 4096 bytes based on the Payload Length Extension field. This parameter change enables the system to flexibly adapt to different data transmission requirements, solving the limitation of insufficient payload length for large data applications.
4Reliability
If edge counting is performed for both TxD and RxD signals and their difference is evaluated, then transmission conflict detection becomes reliable at high data rates, but device complexity increases
Solution Approach 1:
The patent replaces the direct signal comparison mechanism (analog/electrical comparison) with a digital counting and evaluation mechanism. By substituting the direct signal path comparison with edge counting and mathematical evaluation of differences, the system achieves reliable conflict detection at high data rates where direct comparison fails.
Data Source
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AI summary
The invention relates to a device (12; 32) for a serial bus system (1) and to a method for communication in a serial bus system (1). The device (12; 32) has a transmission signal analysis module (151) for counting flanks of a transmission signal (TxD) which is to be transmitted to a bus (40) of the bus system (1) in order to exchange a message (45) between subscriber stations (10, 20, 30) of the bus system (1); a received signal analysis module (152) for counting flanks of a received signal (Rx_In) which is generated from a signal transmitted to the bus (40) on the basis of the transmission signal (TxD), wherein for the message (45), the bus states (401, 402) of the signal in a first communication phase (451; 453, 451) differ from bus states (U_D0, U_D1) of the signal received in a second communication phase (452); and an analysis module (153) for analyzing the difference resulting from a comparison of the flanks counted by the transmission signal analysis module (151) and the flanks counted by the received signal analysis module (152). If the signal transit time on the bus (40) is greater than the bit time (t_b2) of the received signal (Rx_In), the analysis module (153) is designed to signal whether the quantity of the difference is less than or equal to a specified value or whether the quantity of the difference is greater than the specified value, said specified value being greater than null.