CAN Device Queue Credits for Fair Bus Access

The patent segments the message queue into multiple priority levels (first queue and second queue) with different credit thresholds. High-priority messages are placed in the first queue with a higher credit reference value, allowing them to transmit more frequently. Low-priority messages are placed in the second queue with a lower credit reference value, ensuring they still get transmission opportunities. This segmentation resolves the contradiction by allowing both high-speed transmission of urgent messages and timely transmission of less urgent messages.

The patent dynamically adjusts the credit reference values for different queues based on message priority. The first queue (high-priority) has a higher credit reference value than the second queue (low-priority), changing the transmission parameters to favor high-priority messages while still allowing low-priority messages to transmit when their queue credit exceeds their lower reference value. This parameter differentiation resolves the time loss contradiction.

The patent divides the message buffer into two separate queues (first queue and second queue) with distinct credit reference values. Each queue independently manages its own messages and credit counter, simplifying the control logic compared to a single complex queue with dynamic priority adjustment. This segmentation achieves fair access while keeping device complexity manageable.

The patent implements dynamic credit adjustment where the credit counter is decremented by different amounts depending on which queue transmits. When the first queue transmits, the credit decreases by a first value; when the second queue transmits, the credit decreases by a second value. This dynamic behavior achieves fairness without requiring complex real-time priority arbitration logic.