Asynchronous Control Queue With Symmetric Forward and Reverse Latency
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Solution Overview
Problem
Existing asynchronous circuits face challenges in synchronizing component actions due to increasing clock speeds, and there is a need for control queues with equal item flow and bubble flow latencies, which is difficult to achieve with existing designs.
Innovation Solution
A control queue is designed with modules that have equal forward and reverse latencies, constructed using GasP modules, where the present module asynchronously generates outputs based on inputs and alternates polarity, and successive modules alternate between 2-4 and 4-2 GasP configurations, ensuring equal latency for both signal directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If conventional control queue designs are used, then either forward or reverse latency is reduced, but the other latency increases creating asymmetry
Solution Approach 1:
The patent applies asymmetry in reverse - it deliberately designs symmetric latency by using complementary asymmetric modules. The 4-2 GasP module (4 delays forward, 2 delays reverse) is paired with the 2-4 GasP module (2 delays forward, 4 delays reverse) in alternating sequence. This creates overall symmetry where total forward latency equals total reverse latency, resolving the contradiction between reducing one latency direction and maintaining operational balance.
Solution Approach 2:
The control queue is segmented into multiple control modules, each implementing decision-wait functionality. By dividing the queue into discrete modules with specific latency characteristics (4-2 and 2-4 GasP modules), the system can balance overall latency through strategic module selection and arrangement, rather than treating the queue as a monolithic structure.
2Speed
If 4-2 GasP modules are used, then forward latency increases to four delays, but reverse latency decreases to two delays
Solution Approach 1:
The patent uses the 2-4 GasP module as a counterweight to the 4-2 GasP module. The 2-4 module has reversed latency characteristics (2 delays forward, 4 delays reverse) that compensate for the asymmetry introduced by the 4-2 module. When arranged in alternating sequence, these modules counterbalance each other's latency asymmetry, achieving overall symmetric latency performance.
3Productivity
If control queues operate half-full, then balanced latency is most beneficial, but existing designs cannot provide equal forward and reverse latencies
Solution Approach 1:
The patent changes the latency parameters of the control queue by selecting and arranging specific GasP module types (4-2 and 2-4) in alternating sequence. This parameter configuration ensures that the sum of forward delays equals the sum of reverse delays across the entire queue, achieving precise latency equality optimized for half-full queue operation conditions.
Data Source
AI summary
One embodiment of the present invention provides a control queue for an asynchronous circuit that includes a number of control modules coupled together linearly to form the control queue. These control modules include a prior module, a present module, and a next module. The present module is configured to receive one or more forward-going inputs from the prior module and one or more reverse-going inputs from the next module. The present module asynchronously generates one or more forward-going outputs to the next module and one or more reverse-going outputs to the prior module. The modules within the control queue are constructed so that the latency of the forward-going signals through the control queue is equal to the latency of the reverse-going signals through the control queue.