Method for achieving CAM (computer-aided manufacturing) function based on FPGA (Field Programmable Gate Array)

Abstract

The invention discloses a method for achieving the CAM (computer-aided manufacturing) function based on FPGA (Field Programmable Gate Array). The method comprises the following steps: constructing an original CAM data table according to the known conditions, wherein the CAM data table at least comprises a first address entry and a second address entry; constructing a first data table according to the first address entry in the original CAM data table and saving the first data table into an RAM (random-access memory) of the FPGA, wherein the first data table adopts the first address entry as an address index and the second address entry as corresponding data content; and constructing a second data table according to the second address entry of the first data table and saving the second data table into another RAM of the FPGA, wherein the second data table adopts the second address entry as an address index and the first address entry as corresponding data content. According to the method, the internal resource of the FPGA is utilized, all medium-small capacity CAM functions can be achieved, the logic design is simple, the linear speed real-time processing requirement can be met, the method can be flexibly customized and has strong universality, and additional cost is avoided.

Description

technical field [0001] The invention relates to a method for realizing CAM function based on FPGA, which belongs to the technical field of data communication. Background technique [0002] In the field of data communication network and computer Internet, various switches and routers are widely used to realize adaptive conversion and forwarding of data. Generally, data conversion and forwarding can be achieved through a dedicated content addressable memory (CAM: Content Addressable Memory) chip. The lookup table is realized. [0003] With the rapid development of programmable logic device technology, Field Programmable Gate Array FPGA (Field-Programmable Gate Array) has been widely used in various signal processing circuits; at present, the methods for realizing CAM functions based on FPGA mainly include the following Three kinds: [0004] The first is to directly plug in the CAM chip. Because the high price of the CAM chip leads to an increase in the cost of the entire sys...

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Problems solved by technology

[0004] The first is to directly plug in the CAM chip. Because the high price of the CAM chip leads to an increase in the cost of the entire system, and the CAM chip occupies a large area of ​​the circuit board, the CAM chip itself has a large capacity. If only part of the CAM capacity is used, the cost of the CAM chip will be reduced. The utilization rate of the system also reduces the cost performance of the system;

[0005] The second is to use the internal resources of FPGA to design FPGA-CAM according to the logic structure of ASIC-CAM (i.e. register plus comparator structure). This method is complex in logic design and needs to occupy more FPGA resources. It is unacceptable under the circumstances; and because the structure is relatively complex, it generally needs to be implemented with the help of an IP core provided by a third party. This kind of IP core often requires additional payment for intellectual property rights, which increases the cost and is not suitable for low-end FPGA systems;

[0006] The third is to use the internal resources of the FPGA to search and compare items one by one through the state machine polling method to realize the CAM function. This method is similar to software polling. It is time-consuming to realize the CAM function, especially when the CAM capacity increases. Difficult to meet the requirements of real-time wire-speed CAM matching processing

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