Command Decoder Latch Topology for Lower Propagation Delay
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Solution Overview
Problem
As the frequency of clock signals increases to accommodate faster memory operations, propagation delays in semiconductor memories limit operation speed, necessitating techniques to reduce these delays.
Innovation Solution
The implementation of a command decoder with separate flip-flops for different command modes (1N and 2N mode) and alternative logic circuits, such as NAND and NOR logic circuits, reduces propagation delays and provides additional command set-up time by allowing earlier signal transfer between command paths, potentially eliminating the need for multiplexers and reducing delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If clock signal frequency is increased to accommodate faster memory operations, then operation speed is improved, but propagation delays become more significant and limit the operation speed
Solution Approach 1:
The command decoder is divided into multiple independent command paths (first command path and second command path) that can operate simultaneously. Each path has dedicated latches and logic circuits, allowing parallel processing of different command types without interference, thereby reducing overall propagation delay while maintaining high operation speed
Solution Approach 2:
The first latch in each command path latches the command signal earlier in the clock cycle before it would traditionally be processed. This preliminary latching action allows subsequent logic circuits to process commands with more time, reducing critical path delays and enabling faster memory operations
2Productivity
If traditional command decoder architecture is used, then device complexity is maintained at acceptable levels, but propagation delays limit performance
Solution Approach 1:
Multiple command paths are merged into a single command decoder unit with shared output interfaces. The first and second command paths process different command types simultaneously but converge at the output stage, reducing the need for separate decoder units while maintaining parallel processing capabilities and improving throughput
Solution Approach 2:
The command decoder is designed with universal logic circuits that can handle multiple command types through different paths. The same basic latch and logic circuit structures are reused across different command paths with different configurations, reducing overall device complexity while enabling high-performance parallel command processing
Data Source
AI summary
In some examples, command decoders may have multiple command paths. In some examples, command signals from one command path may be provided to another command path from a node located between two latches of the command decoder, such as two latches of a flip-flop. In some examples, the command decoder may include separate flip-flops for different command modes. In some examples, the separate flip-flops may be tristate flip-flops. In some examples, the command decoder may include alternate logic circuits rather than a multiplexer.