Static CMOS Logic CAM Eliminates Precharging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Content-addressable memories (CAMs) face inefficiencies due to the need for precharging at each comparison cycle, leading to reduced operating speed and increased power consumption.
Innovation Solution
A CAM design incorporating static CMOS logic circuits that eliminate the need for precharging by alternating memory units to perform logic operations on comparison results, thereby increasing operating speed and minimizing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If precharging is performed at each comparison cycle, then the CAM can maintain proper voltage levels for comparison operations, but the operating speed is reduced and power consumption is increased
Solution Approach 1:
The patent applies preliminary action by precharging the bit line only once before a sequence of comparison operations rather than precharging before each individual comparison. The bit line is charged to a predetermined voltage level in advance, allowing multiple search operations to proceed without repeated precharging, thus improving speed while maintaining voltage stability
Solution Approach 2:
The patent implements periodic action by structure the comparison operations to occur in batches or sequences between precharging events. Instead of continuous precharging before every operation, the system performs periodic comparison operations using the same precharged bit line until voltage levels require refresh, reducing overall precharging frequency and power consumption
2Reliability
If precharging is performed at each comparison cycle, then the CAM can ensure proper signal levels for accurate comparison, but power consumption is increased
Solution Approach 1:
The bit line is precharged to the required voltage level in advance before a batch of comparison operations. This preliminary precharging action eliminates the need for repeated precharging during subsequent comparisons, significantly reducing power consumption while maintaining the necessary voltage levels for accurate comparison through the retained charge on the bit line capacitance
Solution Approach 2:
The patent maintains continuous useful action by keeping the bit line charged and ready for multiple comparison operations without interruption or re-precharging. The comparison operations continue to utilize the existing voltage level on the bit line, ensuring continuous accurate comparison functionality while minimizing energy expenditure by avoiding repeated precharging cycles
Data Source
AI summary
A CAM includes first and second memory units. The first memory unit includes: a first data memory cell for storing a first data bit; a first comparison circuit for comparing a first search bit with the first data bit to determine if there is a match, and outputting a first comparison result; and a first CMOS logic circuit for performing a logic operation on the first comparison result and outputting a first matching result. The second memory unit includes: a second data memory cell for storing a second data bit; a second comparison circuit for comparing a second search bit with the second data bit to determine if there is a match, and outputting a second comparison result; and a second static CMOS logic circuit for performing a logic operation on the first matching result and the second comparison result, and outputting an output matching result.