Ternary Content Addressable Memory Write Cycle Optimization
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Solution Overview
Problem
Current ternary content addressable memory (TCAM) architectures are insufficient in speed to meet the demands of modern network applications, particularly in write operations, which hinders their applicability in high-speed network devices like switches and routers.
Innovation Solution
The development of TCAM architectures that enable write operations, including data and mask writes, to be performed in a single clock cycle using dedicated buses for data and mask operations, allowing for simultaneous writing and searching with independent masking capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If traditional TCAM architectures are used, then the device can perform search operations, but the write operation speed is insufficient to meet modern network application demands
Solution Approach 1:
The TCAM write operation is segmented into two independent phases within a single clock cycle: data write phase (first edge-triggered) and mask write phase (second edge-triggered). This segmentation allows simultaneous execution of data and mask writes without interference, resolving the speed bottleneck in traditional sequential write architectures.
Solution Approach 2:
The patent implements dynamic clock cycle utilization by employing dual-edge triggering mechanisms. The first edge of the clock cycle triggers data write operations while the second edge triggers mask write operations, dynamically maximizing the utilization of each clock cycle and achieving what would traditionally require two separate clock cycles.
2Reliability
If separate clock cycles are used for data and mask writes, then write operations can be completed, but the overall processing speed is reduced
Solution Approach 1:
The patent merges data write and mask write operations into a single clock cycle by utilizing the two edges of the same clock signal. This combining approach maintains the reliability and completeness of both write operations while eliminating the time loss associated with sequential execution in separate clock cycles.
Solution Approach 2:
The patent employs periodic dual-edge triggering within each clock cycle, where the rising edge triggers data writes and the falling edge triggers mask writes. This periodic action pattern ensures that both write operations are reliably completed while minimizing the total time required, as both operations occur within the regular periodic clock cycle rather than requiring additional cycles.
3Productivity
If dedicated buses are implemented for data and mask operations, then simultaneous writing and searching is enabled, but the device complexity increases
Solution Approach 1:
The patent implements universal buses that can dynamically switch between different functions: during write operations, the buses carry data and mask inputs; during search operations, the same buses carry search keys and control signals. This multi-functionality enables simultaneous writing and searching capabilities while avoiding the need for completely separate dedicated bus architectures, thus managing device complexity.
Data Source
AI summary
Ternary content-addressable memory (TCAM) devices are described. The TCAMs described herein are designed to perform write operations—including data writes and mask writes—in a single clock cycle. For example, data input is written in a row of the TCAM during the first portion of a clock cycle, and a mask is written in another row of the TCAM during the second portion of the clock cycle. In one implementation, a first bus is used both for data write and key search operations, and a second bus is used both for mask write and search masking operations. In another implementation, a first bus is used both for data write and key search operations, a second bus is used for mask write operations, and a third bus is used for search masking operations.