Bidirectional Clock Network Layout for Low-Skew FPGA Timing
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Solution Overview
Problem
Conventional clock network architectures for programmable logic devices are inflexible, leading to increased clock skew and timing uncertainty as devices grow larger, making it difficult to address these issues effectively.
Innovation Solution
The proposed architecture introduces a bidirectional clock network with routing tracks and distribution spines that allow for flexible placement of clock roots within the circuit design, enabling the use of segmented and buffered clock tracks and optional delay elements to null out or equalize clock skew, thereby reducing skew and hold timing issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional regional and global clock architectures are used, then the clock network structure is simple, but clock skew and timing uncertainty increase as the device size grows
Solution Approach 1:
The clock network is divided into multiple hierarchical levels including global clock distribution, regional clock domains, and local clock buffering. This segmentation allows the large device to be managed as smaller manageable regions, reducing overall clock skew while maintaining structural organization.
Solution Approach 2:
The patent introduces bidirectional clock routing that operates in multiple dimensions across the device fabric. Clock signals can propagate in both directions through the routing infrastructure, adding spatial flexibility to the clock distribution network and enabling more precise timing control across large device areas.
2Device complexity
If clock roots are fixed at specific locations (edge for regional, center for global), then the routing structure is simplified, but flexibility to address clock skew issues is reduced
Solution Approach 1:
The routing tracks are designed to serve multiple functions: they can carry clock signals bidirectionally, support multiple potential clock root locations, and adapt to different clock distribution patterns. This universal routing infrastructure replaces the need for fixed, dedicated routing paths.
Solution Approach 2:
The clock network architecture allows dynamic selection of clock root locations and adaptive routing paths. The system can reconfigure clock distribution based on the specific timing requirements and device layout, rather than being constrained to predetermined fixed paths.
3Reliability
If bidirectional routing tracks and distribution spines are implemented, then clock skew can be reduced through flexible routing, but the device complexity increases
Solution Approach 1:
The patent merges the routing track and distribution spine functions into a unified bidirectional infrastructure. This consolidation reduces the total number of separate routing elements needed while maintaining the capability for flexible, low-skew clock distribution through bidirectional signal propagation.
Data Source
AI summary
An apparatus includes an integrated circuit with a clock network in an array of circuit blocks. The clock network includes routing tracks, distribution spines, and clock leaves. The routing tracks and the distribution spines are bidirectional.