Memory Command Decoder Paths 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, reduces propagation delays and provides additional command set-up time by allowing signal transfer between command paths sooner, potentially eliminating the need for multiplexers and reducing the risk of invalid command latching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If clock signal frequency is increased to accommodate faster memory operations, then memory operation speed is improved, but propagation delays become more significant and limit further speed increases
Solution Approach 1:
The command decoder is divided into separate command paths (e.g., even and odd paths) with dedicated flip-flops for each path. This segmentation allows independent optimization of each path's timing characteristics, reducing overall propagation delay by eliminating the need for multiplexer switching between paths.
Solution Approach 2:
Command signals are pre-positioned in separate flip-flops along different command paths before being needed. This preliminary action allows the system to prepare command signals in advance without waiting for multiplexer switching, thereby reducing propagation delay and enabling faster memory operations.
2Speed
If conventional command decoder architecture is used, then device complexity is maintained at acceptable levels, but propagation delays limit operational speed
Solution Approach 1:
Multiple command paths are merged into a unified decoder architecture that shares common logic resources while maintaining separate signal paths. This merging approach reduces overall device complexity compared to having completely separate decoders for each path, while still achieving reduced propagation delays through the elimination of multiplexer switching.
3Reliability
If signal transfer between command paths is delayed, then timing stability is improved, but command set-up time is reduced
Solution Approach 1:
Dedicated flip-flops serve as intermediary elements that hold command signals in separate command paths. These intermediary flip-flops ensure that signals are transferred at the correct timing without requiring delayed transfer mechanisms, thereby maintaining timing stability while maximizing command set-up time availability.
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.