Isochronous Synchronizer Phase Alignment Circuit
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Solution Overview
Problem
Existing synchronization methods between clock environments with unknown phase relationships incur unnecessary delays and inefficiencies, particularly when clock frequencies are not identical, leading to metastability issues and increased latency in communication systems.
Innovation Solution
The implementation of a circuitry and method that generates timing signals with varying delays in one clock environment and samples them in another, allowing for the generation of a control signal to optimize the transfer time of a change of state, thereby avoiding synchronizer delays and metastability risks, even when clock frequencies are nominally the same but have an unknown phase relationship.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional synchronizers are used to capture signals crossing clock boundaries, then metastability issues are avoided, but unnecessary delays are incurred and communication efficiency is reduced
Solution Approach 1:
The patent changes the parameter of clock frequency relationship from completely asynchronous to isochronous (same frequency, unknown phase). By establishing that clocks have the same frequency, the system can use phase alignment techniques rather than traditional multi-cycle synchronizers, reducing delay while maintaining metastability avoidance.
Solution Approach 2:
The patent replaces the mechanical/time-based waiting approach of traditional synchronizers (waiting multiple clock cycles) with a phase-detection and alignment mechanism. The phase detector identifies the phase relationship, and the delay element adjusts timing dynamically, substituting blind waiting with intelligent timing control.
2Reliability
If the number of clock cycles is increased to meet metastability settling time for varying clock frequencies, then reliability is improved, but latency increases unnecessarily for lower clock frequencies
Solution Approach 1:
The patent introduces dynamic phase adjustment through delay elements that can be programmably configured. Instead of using a fixed number of clock cycles for synchronization, the system dynamically adjusts the delay based on the actual phase relationship detected, optimizing the settling time for each specific operating condition rather than preparing for the worst-case scenario always.
Solution Approach 2:
The patent implements a feedback mechanism where the phase detector continuously monitors the phase relationship between isochronous clocks and provides information to the delay element control. This feedback loop allows the system to adaptively adjust timing parameters to maintain optimal synchronization without excessive delay.
3Area of stationary object
If control signals are passed through synchronizers instead of individual data signals, then area overhead is reduced, but delay is still incurred for all associated signals
Solution Approach 1:
The patent extracts the synchronization function from the data path by using a separate phase detector and control signal mechanism. The phase detection and delay adjustment are performed independently of the actual data signals, allowing data to be transferred without passing through traditional synchronizer flip-flops, thus eliminating the delay for data signals while maintaining area efficiency.
4Reliability
If traditional synchronizers are used for signals crossing clock boundaries with unknown phase relationships, then timing safety is ensured, but bandwidth utilization is reduced and communication efficiency decreases
Solution Approach 1:
The patent performs preliminary phase detection and delay calibration before actual data transfer begins. By establishing the phase relationship and configuring the delay elements in advance, the system ensures timing safety is already arranged, allowing subsequent data transfers to proceed without additional synchronization delays, thus maximizing bandwidth utilization.
Data Source
AI summary
Circuitry for synchronizing communications between clock environments wherein a change of state is transmitted from a first clock environment to a second clock environment, the first clock environment being timed by a first clock signal and the second clock environment being timed by a second clock signal, the first and second clock signals having nominally the same frequency but an unknown phase relationship, the circuitry comprising: delay means in the first clock environment arranged to generate a plurality of timing signals by delaying said first clock signal by respectively different delay values; sampling means in the second clock environment for sampling said plurality of timing signals at timing determined by said second clock signal thereby generating a plurality of sampled timing signals; and determining means for generating a control signal based on said plurality of sampled timing signals and outputting said control signal for controlling the transfer time of said change of state.