Patent ID: 7525827

Claim:
A stored don't-care based hierarchical search-line scheme used in a content-addressable memory comprising: a plurality of blocks divided from said content-addressable memory, each said block containing a memory cell and storing a plurality of don't cares which have defined don't-care states; a plurality of hierarchical search-line groups disposed in said blocks, each said hierarchical search-line group including a global search-line and a local search-line, said local search-line being connected to said memory cell, each said block searching synchronously said don't-cares; a plurality of buffers, each said buffer being disposed in one of said block and connected to said global search-line and said local search-line, said don't-care state being based to determine whether to transfer data on said global search-line to said local search-line or not; data of said content-addressable memory are stored in order in said block according to length of prefix of the data; all said local search-lines in a same column of said blocks are connected to a common global search-line, and input search data are sent to said global search-line at every search cycle; and said don't-cares are data stored at top of said memory cell in each said block.