1-Wire Subordinate Device Delay for Valid Read Synchronization
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Solution Overview
Problem
In one-wire and two-wire protocols, the bus park duration is insufficient for subordinate devices to prepare data, leading to invalid data retrieval by principal devices, necessitating multiple read requests that reduce throughput and increase latency.
Innovation Solution
Implementing a local clock and protocol controller at the subordinate device to manage a delay window greater than a clock cycle, allowing synchronization pulses and data transmission only after the data is ready, thereby extending the bus park if necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the bus park duration is kept short (one clock cycle), then the communication speed is improved, but the subordinate device cannot prepare data in time leading to invalid data retrieval
Solution Approach 1:
The bus park duration is made dynamic rather than fixed at one clock cycle. The protocol controller extends the bus park duration adaptively based on whether the subordinate device has prepared the data ready, allowing the system to optimize between speed and reliability for each transaction
Solution Approach 2:
The subordinate device uses the bus park period to preliminarily prepare the data before the actual read operation. By extending the bus park duration, the device has sufficient time to complete data preparation in advance, ensuring valid data is ready when the principal device performs the read
2Reliability
If multiple read requests are sent to retrieve valid data, then the data validity is improved, but the throughput decreases and latency increases
Solution Approach 1:
The subordinate device performs data preparation during the bus park period before the principal device executes the read command. This preliminary action ensures that valid data is already ready when needed, eliminating the requirement for multiple retry read requests and thereby maintaining high throughput
3Reliability
If multiple read requests are sent to retrieve valid data, then the data validity is improved, but the latency increases
Solution Approach 1:
Data preparation is performed preliminarily during the extended bus park period before the read command is executed. This eliminates waiting time and redundant read requests, thereby reducing latency while ensuring data validity
4Reliability
If the bus park duration is extended to allow data preparation, then the data validity is improved, but the communication speed decreases
Solution Approach 1:
The bus park duration is dynamically adjusted based on actual data preparation needs rather than being uniformly extended. The protocol controller monitors data readiness and terminates the bus park period appropriately, minimizing unnecessary time extension while ensuring data validity
Data Source
AI summary
A subordinate device includes a local clock and a protocol controller. The protocol controller is coupled to a bus that includes a data wire. The protocol controller is configured to receive, on the data wire from a principal device, a read command addressed to the subordinate device indicating initiation of a read transaction. The protocol controller is also configured to, after a delay window, send synchronization pulses to the principal device based on the local clock, where a duration of the delay window is greater than a clock cycle of the local clock. The protocol controller is further configured to, after sending the synchronization pulses, send data on the data wire to the principal device based on the local clock during the read transaction.