Wired Bus Arbitration Using Sequential ID Queries
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Solution Overview
Problem
Existing arbitration methods in wired bus systems face challenges with oscillator tolerance, requiring precise timing and complex protocols, leading to unreliable arbitration due to timing errors and overlapping decision windows, especially during network initialization.
Innovation Solution
A method for assigning unique network addresses to responders using a commander-responder configuration, where the commander sends a subset of bits from the ID space, responders check for matches, and upon collision, adjust the query value, ensuring each responder is uniquely identified without requiring expensive hardware or complex protocols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional arbitration methods using precise crystal oscillators are used, then timing accuracy is improved, but device cost and complexity increase
Solution Approach 1:
The patent replaces expensive crystal oscillators with inexpensive RC oscillators in responder devices. The system accepts that RC oscillators have lower precision and shorter effective timing windows, but compensates through a different arbitration approach where the commander device (with precise oscillator) coordinates the arbitration process, allowing responders to use cheaper timing components without compromising overall system reliability.
Solution Approach 2:
The patent changes the arbitration parameter from relying on simultaneous transmission windows (which require tight oscillator matching) to a sequential query-based approach. The commander sends query messages with specific ID values, and responders respond in turn, transforming the timing-critical parallel arbitration into a time-managed sequential process that tolerates wider oscillator variations.
2Adaptability or versatility
If sequential query-based arbitration is used, then oscillator tolerance is improved, but arbitration time increases
Solution Approach 1:
The commander device pre-organizes the arbitration process by sequentially sending query messages with specific ID values before actual data transmission begins. This preliminary identification phase establishes the transmission order in advance, allowing the system to tolerate slower arbitration times during setup while maintaining efficient operation during actual data communication.
Solution Approach 2:
The arbitration process uses periodic query messages from the commander, sending questions at regular intervals with different ID values. This periodic approach structures the arbitration time into manageable cycles, making the extended arbitration time predictable and acceptable, especially since it only occurs during network initialization or reconfiguration.
3Reliability
If collision detection and retry mechanism is implemented, then arbitration reliability is improved, but communication overhead increases
Solution Approach 1:
The system implements feedback through collision detection where responders monitor the bus during transmission. When a collision is detected (indicating multiple responders attempted to transmit simultaneously), the system sends a non-acknowledgment message back to the commander, triggering a retry with adjusted timing or ID values. This feedback loop ensures reliable arbitration while keeping overhead minimal through targeted retries rather than continuous communication.
Data Source
AI summary
A method of assigning an address on a wired network includes at least one commander and a plurality of responders is provided. A value of a subset of bits sent by the commander is compared with the ID of each responder. The responders that find a match send their IDs or a part of their ID. If there is a collision, a new value is sent. If only one responder has a match, the commander assigns that responder a node address which is shorter than the ID.