PLL Core Reset Synchronization for High-Speed Interface Latency
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Solution Overview
Problem
The synchronization of high-speed data transfer between digital cores and physical interfaces in modern digital circuit applications is challenging due to signal latency and metastability issues, particularly in applications requiring multiple parallel high-speed serial channels, where existing solutions like first-in-first-out structures or direct core-to-physical interface data delivery either increase latency or accept metastability.
Innovation Solution
The apparatus and method involve using a phase-locked-loop (PLL) to synchronize a core reset signal with a physical interface clock, generating a sampled reset signal that aligns the physical interface clock with the core clock, reducing latency and metastability by ensuring a known time relationship and phase accuracy between the clocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If data is routed from the core to multiple separated physical interfaces, then the data transfer capability is improved, but signal latency increases due to physical separation and routing distance
Solution Approach 1:
The patent divides the data transfer system into multiple independent parallel channels, each with its own clock generation and synchronization logic. This segmentation allows data to be routed to multiple physical interfaces simultaneously without the latency penalty of sequential processing, as each channel operates independently with locally generated clocks that are synchronized to the core clock.
Solution Approach 2:
The patent implements preliminary synchronization by generating local clocks at each physical interface that are预先 synchronized to the core clock using phase-locked loops. This preliminary clock synchronization ensures that when data arrives at each interface, the timing is already aligned, eliminating the need for additional latency-inducing synchronization delays.
2Measurement precision
If a globally routed physical interface clock is used to synchronize data transfer, then timing alignment is improved, but metastability problems increase at the core-to-physical interface boundary
Solution Approach 1:
The patent implements local clock generation at each physical interface using phase-locked loops that are locally synchronized to the core clock. This local approach maintains precise timing alignment while avoiding the metastability problems associated with globally routed clocks, as each local clock is independently stabilized and phase-aligned without requiring long-distance signal routing.
Solution Approach 2:
The phase-locked loop acts as an intermediary between the core clock and the physical interface clock. It receives the core clock signal, processes it through feedback control, and generates a locally synchronized clock signal that is phase-aligned with the core clock but generated locally, thereby eliminating direct metastability issues at the interface boundary.
3Measurement precision
If a first-in-first-out structure is used to ensure data handoff synchronization, then timing synchronization is improved, but latency increases due to the additional buffering structure
Solution Approach 1:
The phase-locked loop serves as an intermediary that directly synchronizes clock phases without requiring FIFO buffering structures. By using feedback control to align the phase of local clocks with the core clock, the system achieves precise data handoff synchronization while avoiding the latency introduced by read/write pointer management and buffer storage operations.
Solution Approach 2:
The patent replaces the mechanical FIFO buffering approach with a phase-based synchronization mechanism using phase-locked loops. Instead of storing data in buffers and managing pointers, the system uses phase-aligned clocks to ensure data arrives at the correct time, eliminating the need for latency-inducing buffering structures.
Data Source
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AI summary
In one example implementation, the present disclosure provides a system that includes circuitry and one or more electronic components for synchronizing data transfer from a core to a physical interface. One example can involve an apparatus for interfacing a digital core with at least one physical interface that includes a macro configured on the digital core, the macro having at least one data output, a first data input, a reset input and a sync reset output, the macro to be clocked by a first clock having a first clock rate. The first clock can be configured to clock in data from the digital core on the first data input; clock in a reset signal from the digital core on the reset input, wherein a synchronized reset signal is output on the sync reset output. The apparatus can also include physical interface circuitry and a reset sampling input.