Associative memory device and network frame switch

Abstract

The present invention provides a network frame switch and a content addressable memory (CAM). The CAM includes a plurality of word memories which store a plurality of data pieces in such a way that those data pieces can be rewritten and registers which corresponding to the plurality of word memories respectively. The registers store information indicating whether valid target data is stored in the corresponding word memories, so that when retrieval data is input, the system retrieves word memories that store target data having a data part whose position corresponds to a prescribed first data part extracted from the input retrieval data. The CAM further includes a retrieval result correspondence write-in device which performs retrieval of word memories which store target data comprising a data part whose position corresponds to the first data part. Depending on whether any word memories are detected, the data part whose position corresponds to a second data part that is different from the first data part and which is extracted from the input retrieval data out of the target data stored in one or more word memories selected from the detected word memories, is overwritten by the same information as the second data part or the input retrieval data is written in one word memory selected from one or more word memories other than the word memory storing valid target data using the retrieval result correspondence write-in device.