AQFP Circuit Placement With Multi-Phase Clock Alignment
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Solution Overview
Problem
Existing electronic design automation (EDA) tools are inadequate for placing superconducting electronics (SCE) circuits that utilize multiple clock phases, such as adiabatic quantum flux parametron (AQFP) circuits, due to differences in clock signal distribution and phase requirements, leading to inefficiencies and the need for specialized tools.
Innovation Solution
Adapt CMOS placement tools to accommodate multi-phase clock signals in SCE circuits by ensuring all output ports are associated with the same clock phase through levelized placement, buffer insertion, and row splitting, while adhering to constraints like maximum net length and row bounds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If existing EDA tools are used for placing SCE circuits with multiple clock phases, then the placement process is simplified, but the clock phase alignment and signal integrity cannot be ensured
Solution Approach 1:
The placement process is segmented into multiple passes: initial placement using standard EDA tools, followed by specialized post-processing steps including buffer insertion and row splitting. This segmentation allows leveraging existing tools while adding targeted functionality to handle clock phase requirements.
Solution Approach 2:
Buffers are inserted as intermediary elements between cells to adjust clock phase alignment. These buffers act as mediators that synchronize clock signals across different rows and columns, ensuring proper phase alignment without requiring complete redesign of the placement process.
2Reliability
If levelized placement with buffer insertion is implemented, then clock phase alignment is ensured, but the placement complexity increases
Solution Approach 1:
The netlist is levelized during the design phase before physical placement, organizing cells into logical groups based on their clock phase requirements. This preliminary organization simplifies subsequent placement steps by pre-grouping cells that share the same clock phase, reducing the complexity of the actual placement process.
Solution Approach 2:
The placement process is made dynamic through iterative row splitting and buffer insertion. The algorithm adapts the floorplan structure during placement, dynamically adjusting row configurations and inserting buffers where needed, rather than following a rigid predetermined structure.
3Reliability
If row splitting is performed to accommodate clock phases, then clock distribution is improved, but the floorplan area increases
Solution Approach 1:
Row splitting is applied locally only where clock phase alignment requirements demand it, rather than uniformly across the entire floorplan. This selective approach ensures proper clock distribution in critical areas while minimizing the overall area impact.
Solution Approach 2:
Multiple rows that require the same clock phase are merged into unified placement regions, allowing shared clock distribution infrastructure. This merging reduces redundant clock routing and minimizes the additional area required for clock distribution networks.
4Reliability
If maximum net length constraints are enforced, then signal integrity is improved, but the placement flexibility is reduced
Solution Approach 1:
Buffers are strategically inserted as intermediary elements to extend the effective driving capability of cells. These buffers act as signal repeaters that maintain signal integrity over longer distances, allowing greater placement flexibility without compromising signal quality.
Solution Approach 2:
The placement process continuously monitors and enforces maximum net length constraints during cell positioning, rather than applying them as fixed boundaries. This continuous adjustment maintains signal integrity while adapting to placement opportunities, preserving flexibility within the constraints.
Data Source
AI summary
Cells in a superconducting electronics (SCE) netlist may be levelized. The SCE may use multiple clock phases, and each level in the levelized SCE netlist may be associated with a clock phase. Buffers may be inserted in the SCE netlist so that output ports of the SCE netlist are associated with the same clock phase. A floorplan may be created for the SCE netlist. A placed SCE netlist may be generated based on the floorplan, where cells in each row of the placed SCE netlist may be clocked using the same clock phase.