Single-Pin SYSREF Windowing for Glitch-Free Clock Synchronization
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Solution Overview
Problem
Clock generation/distribution devices often face challenges in synchronizing load clocks without setup or hold violations, especially in pin-limited devices where separate pins for synchronization and SYSREF signal generation are not available, leading to potential glitches and synchronization issues.
Innovation Solution
A system and method utilizing a single pin interface for both synchronization and SYSREF generation, employing a windowing scheme to determine the position of the SYSREF signal with respect to a clock edge, providing a delayed replica within a reliable timing window, and allowing simultaneous windowing and SYSREF generation without glitches, ensuring deterministic synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate pins are used for synchronization and SYSREF signal generation, then synchronization reliability is improved, but device complexity increases
Solution Approach 1:
The patent combines synchronization and SYSREF signal generation functions into a single pin interface. The capture circuit samples the control signal at specific clock edges to differentiate between synchronization mode (sampled at rising edge) and SYSREF generation mode (sampled at falling edge), eliminating the need for separate pins while maintaining functional reliability
Solution Approach 2:
The single pin is designed to serve multiple functions: it can trigger synchronization events, generate SYSREF signals, and support windowing operations. The system dynamically switches between these functions based on the sampling results and mode selection, making the pin universal rather than dedicated to a single purpose
2Device complexity
If a single pin is used for both synchronization and SYSREF generation, then device complexity is reduced, but signal timing precision deteriorates
Solution Approach 1:
The patent segments the control signal processing into distinct time windows and sampling points. The capture circuit samples at specific clock edges (rising or falling) to create separate processing paths for synchronization and SYSREF generation, ensuring that each function receives precisely timed signals without interference
Solution Approach 2:
The system performs preliminary sampling of the control signal at defined clock edges before generating the actual output signals. This preliminary action at the capture circuit stage establishes deterministic timing relationships, allowing the system to prepare synchronization or SYSREF signals in advance with precise timing control
3Manufacturing precision
If windowing is performed to determine SYSREF position, then timing precision is improved, but device complexity increases
Solution Approach 1:
The patent introduces a time-domain dimension to the control signal processing by implementing windowing. The system divides the clock cycle into specific time windows and samples the control signal at predetermined points within these windows, adding temporal structure to the signal processing without requiring additional hardware pins
Data Source
AI summary
In an example, a system is adapted to be coupled to a load device having a load clock. The system includes a clock generation device with a pin. The system also includes a capture circuit coupled to the pin and operable to sample a value at the pin. The system includes a D flip-flop having a data input coupled to the capture circuit, a clock input coupled to a clock, and having an output, where the D flip-flop is operable to provide, at the output, a system reference event (SYSREF) signal to align the load clock to the clock, based at least in part on the value at the pin.