RQL Circuit Synthesis Using Placeholder Flip-Flops and Clock Phasing
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Solution Overview
Problem
Current CMOS synthesizers struggle to efficiently design Reciprocal Quantum Logic (RQL) circuits, particularly due to the inability to replicate edge-triggered flip-flop devices, which are essential for synchronous design methodologies, as they require sequential FF elements not available in typical RQL component libraries.
Innovation Solution
A synthesis tool method that generates RQL netlist circuits by using a placeholder flip-flop device, replacing it with sequentially controlled flip-flop devices phased according to a clock signal, and separating the circuit system into subsystems associated with each phase, allowing for the removal of flip-flop devices to create a functional RQL circuit design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a placeholder flip-flop device is used in RQL circuit synthesis, then the circuit can be designed with clock-triggered flip-flop capabilities, but the device complexity increases due to the need for sequential FF elements and phase separation
Solution Approach 1:
The patent uses a placeholder flip-flop device as an intermediary element that enables CMOS synthesis tools to work with RQL circuits. This placeholder serves as a mediator between the synthesis tool's expectation of sequential FF elements and the actual RQL implementation that uses Josephson transmission lines and phase-separated circuit subsystems instead of traditional flip-flops
Solution Approach 2:
The patent divides the RQL circuit into multiple circuit subsystems, each associated with a separate phase of a clock signal. This segmentation allows the circuit to emulate flip-flop functionality through phase-separated logic elements rather than requiring traditional sequential FF devices, thus achieving adaptability while managing complexity through modular organization
2Reliability
If the circuit system is separated into multiple subsystems associated with different clock phases, then proper phase sequencing is achieved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent implements dynamic phase sequencing where circuit subsystems are associated with different phases of a clock signal. This dynamic approach allows reliable timing control and phase sequencing essential for RQL operation, while the automated synthesis tool manages the complexity of assigning and coordinating these phases across multiple subsystems
3Productivity
If sequential flip-flop devices are replaced with RQL logic elements, then the circuit operates efficiently in RQL, but the synthesis tool cannot directly support the design
Solution Approach 1:
The patent creates a virtual copy of the flip-flop functionality using a placeholder device in the synthesis tool. This placeholder replicates the behavioral interface of a sequential FF element, allowing the synthesis tool to automatically optimize the circuit while the actual RQL implementation uses equivalent logic elements built from Josephson transmission lines and phase-separated subsystems
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables the design and optimization of RQL circuits with clock-triggered flip-flop capabilities, overcoming the limitations of existing synthesis tools by emulating flip-flop functionality and ensuring proper phase sequencing through Josephson transmission lines, thus facilitating efficient RQL circuit synthesis.
Implementation Method 1
ensuring proper phase sequencing through Josephson transmission lines
Data Source
AI summary
One embodiment of the invention includes a method for generating a Reciprocal Quantum Logic (RQL) circuit design via a synthesis tool. The method includes providing data associated with behavior and constraints of the RQL circuit design and a component library to the synthesis tool. The method also includes generating an RQL netlist circuit comprising a flip-flop device placeholder and a circuit system coupled to at least one of an input and an output of the flip-flop device placeholder via the synthesis tool based on the data and a component library. The method also includes separating the circuit system into circuit subsystems that are each associated with a separate respective phase of a clock signal via the synthesis tool based on inputs. The method further includes removing the flip-flop device placeholder from the RQL netlist circuit via the synthesis tool to generate the RQL circuit design from the RQL netlist circuit.