I2C Bus Low State Duration Detection Calibration
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Solution Overview
Problem
Existing methods for detecting the duration of the low state of a synchronization signal in an I2C bus, particularly in SMBus, face challenges due to manufacturing dispersions and require calibration to accurately determine if the low state exceeds a predetermined time period, which can lead to inconsistent detection across identical circuits.
Innovation Solution
A method that compares the duration of the low state of the synchronization signal with a threshold stored in a non-volatile memory, calibrated during initialization, using an oscillator and counter to determine the longest duration before data transmission, ensuring accurate detection by updating values synchronously with the signal and reading the threshold during the first byte transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a fixed threshold is used for detecting the low state duration without calibration, then the detection process is simple, but manufacturing dispersions cause inconsistent detection results across identical circuits
Solution Approach 1:
The patent applies preliminary action by performing calibration during the initialization phase before normal operation. The threshold is adjusted based on the actual low state duration measured during initialization, ensuring that each circuit is pre-configured to account for manufacturing variations. This preliminary calibration action resolves the contradiction by establishing reliable detection parameters before the system enters its operational state.
2Reliability
If calibration is performed to account for manufacturing variations, then detection consistency is improved, but the device complexity increases due to additional calibration circuitry and procedures
Solution Approach 1:
The patent merges the calibration function with the existing initialization sequence and uses the same hardware resources (oscillator, counter, and register) that are already part of the low state duration detection mechanism. By combining the calibration process with the initialization routine and reusing existing components, the patent achieves detection consistency without significantly increasing device complexity.
3Productivity
If the threshold is read from memory during the first byte transmission, then the calibration is integrated into normal operation, but the detection of the low state duration must be completed before the acknowledgment time
Solution Approach 1:
The patent maintains continuity of useful action by performing the low state duration measurement and threshold comparison during the byte transmission process itself. The measurement continues throughout the transmission, and the comparison is completed before the acknowledgment is due, ensuring that the detection process is both integrated into normal operation and completed within the required time constraints.
Data Source
AI summary
A value representative of a duration of the low state of a synchronization signal on a bus is measured and then compared with a threshold value. The threshold value is stored in a memory and the measured value represents, in a first comparison, a longest duration of the low states of the synchronization signal.