Reversible D Latch Circuit With Fewer Gates and Garbage Outputs
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Solution Overview
Problem
Conventional logic gates are generally irreversible, leading to high implementation costs and power consumption in reversible circuit design, particularly when implementing reversible sequential apparatuses like D latches, which require a large number of gates and garbage outputs.
Innovation Solution
A reversible sequential apparatus is designed using a minimal number of gates, specifically comprising a configuration of Toffoli gates and Fredkin gates, where additional outputs are used as garbage bits to achieve reversibility, reducing the number of gates and garbage outputs required, and employing an augmented truth table method to extend the original irreversible truth table into a reversible one.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional direct transformation method is used to implement reversible D latch, then the latch can be constructed from irreversible gates, but the number of gates and garbage outputs increases significantly
Solution Approach 1:
Instead of directly transforming irreversible gates to reversible gates (conventional approach), the patent inverts the approach by starting with reversible gate primitives (NOT, CNOT, Toffoli, Fredkin) and constructing the D latch functionality from them. This inversion of the design methodology enables minimal gate usage while maintaining reversibility, resolving the contradiction between ease of implementation and device complexity.
2Ease of manufacture
If conventional direct transformation method is used to implement reversible D latch, then the latch can be constructed from irreversible gates, but the number of garbage outputs increases significantly
Solution Approach 1:
The patent inverts the conventional transformation approach by building reversible D latch directly from reversible gate primitives rather than transforming irreversible gates. This inversion minimizes garbage outputs because the design starts with reversible operations that inherently produce fewer unwanted outputs, while still achieving the desired latch functionality.
3Reliability
If more gates are used to achieve reversibility, then the sequential apparatus can maintain functionality, but the implementation cost and power consumption increase
Solution Approach 1:
The patent changes the parameter of gate selection from conventional irreversible gates to specific reversible gates (NOT, CNOT, Toffoli, Fredkin) with optimized configurations. By carefully selecting and configuring these reversible gates, the patent achieves the required reversibility while minimizing the total number of gates, thereby reducing implementation cost and power consumption associated with operating these gates.
4Reliability
If more gates are used to achieve reversibility, then the sequential apparatus can maintain functionality, but the implementation cost increases
Solution Approach 1:
The patent optimizes the parameters of the reversible circuit by selecting specific gate types (NOT, CNOT, Toffoli, Fredkin) and configuring them in minimal configurations. This parameter optimization achieves the required reversibility while minimizing the number of gates and garbage outputs, thereby reducing implementation cost without sacrificing functionality.
Data Source
AI summary
A reversible sequential apparatus comprises a first logic gate and a second logic gate. The first logic gate includes first, second and third input terminals and first, second and third output terminals. The second logic gate includes first and second input lines and first and second output lines. The first input terminal for carrying a clock signal is coupled to the first output terminal and the second input terminal for carrying an input signal is coupled to the second output terminal. When the first input terminal and the second input terminal are simultaneously set to a first state, the level of the third output terminal is inverse to the level of the third input terminal; otherwise, the level of the third output terminal is identical to the level of the third input terminal. The third output terminal, second input line and second output line are coupled to each other. The input signal carried on the first input line is set to a constant level so that the second output line and the first output line have the same outputs.