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 (,), an associative memory with a shortest mask producing function carries out logical multiplication for all of mask information corresponding to the coincident storage data with a mask valid state as true. The result of logical multiplication is used as shortest mask information. In a primary searching operation, the associative memory with a shortest mask producing function is supplied with the search data (,) to provide the shortest mask information on shortest mask lines. Then, as a secondary searching operation, the shortest mask information thus extracted is used as the search data and supplied to the associative memory with a shortest mask producing function. Among the coincident storage data, only a mask match line connected to a particular word having mask information coincident with the shortest mask information is selected as the secondary search result. The associative memory is used in a network router, to calculate an optimum memory address signal (,) by encoding the selected mask match line. In response to the memory address signal (,), a memory data signal (,) enabling shortest network connection is produced as a transfer network address (,). The transfer network address (,) is combined with a data area (,) and a destination network address (,) contained in input transfer data (,) to produce output transfer data (,).