Strobe Clock Switching for Wide-Range Source-Synchronous Reads

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Solution Overview

Problem

Integrated circuits face challenges in synchronizing with strobe signals over a wide range of frequencies due to the large area consumption of delay lines, especially when dealing with lower frequency signals, and the inadequacy of strobe signals to complete data propagation to destination subsystems.

Innovation Solution

A system that includes a pulse controller to count pulses and replace the strobe signal with a phase and frequency-aligned reference signal, using a delay line and frequency dividers to achieve synchronization, allowing for adjustable delay and phase alignment, thereby reducing the need for extensive delay lines and ensuring complete data propagation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a delay line is used to synchronize with lower frequency strobe signals, then synchronization capability is improved, but area consumption increases

Engineering Contradiction:

Improvesynchronization capabilityVSAvoidarea consumption

Core Design Contradiction:

Adaptability or versatilityVSArea of stationary object

Solution Approach 1:

The system pre-generates multiple phase-shifted versions of the strobe signal using parallel delay paths before they are needed for synchronization. This allows the target to quickly select the appropriate phase without requiring a large, area-consuming delay line to generate phases on-demand during operation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The delay line is divided into multiple smaller segments or stages, each contributing a portion of the total delay. Multiple parallel segments operate simultaneously to generate different phase versions, reducing the area required compared to a single long delay line while maintaining the full range of phase coverage.

Inventive Principle:

Principle #1Segmentation

2Area of stationary object

If the strobe signal stops providing pulses when data stops, then area consumption is reduced, but data propagation completeness deteriorates

Engineering Contradiction:

Improvearea consumptionVSAvoiddata propagation completeness

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The system maintains continuous operation of the strobe signal generation and distribution infrastructure even when data transfer temporarily stops. By keeping the phase-aligned reference signal path active and ready, the system ensures that data propagation can resume immediately without interruption, maintaining reliability while avoiding the need for large buffers or re-synchronization mechanisms that would increase area.

Inventive Principle:

Principle #20Continuity of useful action

Data Source

PatentUS8446195B2Strobe signal management to clock data into a system

Publication Date: 2013.05.21 XILINX INC

AI summary

A method of communicating with a source synchronous device can include determining an expected number of pulses of a strobe signal to be received in response to a first read request directed to the source synchronous device and receiving the strobe signal from the source synchronous device. Pulses in the strobe signal can be counted. Responsive to detecting a last pulse of the expected number of pulses of the strobe signal, the strobe signal can be replaced with a reference signal that is phase and frequency aligned with the strobe signal.