Associative memory having a mask function for use in a network router

Abstract

When one or more storage data are coincident with single search data ( 12 ), an associative memory ( 1 ) carries out logical sum for all of storage data with a valid state for storage data as true. The result of logical sum is used as matched data logical-OR information. In a primary searching operation, the associative memory ( 1 ) is supplied with the search data ( 12 ) to provide the matched data logical-OR information on matched data logical-OR lines. Then, the associative memory ( 1 ) carries out a secondary searching operation supplied as search data with the matched data logical-OR information obtained by all of storage data coincident upon the primary searching operation. Only a match line ( 5 ) coincident with the matched data logical-OR information is selected as the secondary search result. The associative memory is used in a network router to calculate an optimum memory address signal ( 403 ) by encoding the selected match line ( 5 ). In response to the memory address signal ( 403 ), a memory data signal ( 405 ) enabling shortest network connection is produced as a transfer network address ( 413 ). The transfer network address ( 413 ) is combined with a data area ( 412 ) and a destination network address ( 411 ) contained in input transfer data ( 408 ) to produce output transfer data ( 409 ).

1 . An associative memory which stores mask information for each of one or more words of storage data to indicate a valid state or an invalid state representative of whether or not each of one or more bits of said storage data should be excluded from a search object, said associative memory carrying out, when one or more of said words are selected as data that should be selected using external search data in a primary searching operation for each word, in which said mask information is taken into account in order to exclude from a search object those one or more bits of said storage data for which the corresponding mask information is in a valid state, a logical operation of the storage data of said selected words.  
   
   
       2 - 19 . (canceled)