Content-addressable memory module with associative clear

Abstract

A content-addressable memory module which performs an associative clear operation in response to a clear signal provided on a clear line. The associative clear operation simultaneously clears all registers in the content-addressable memory module whose contents match bits in a pattern input to the content-addressable memory module. A mask input along with the pattern determines which bits of the pattern are significant for the match. Each register in the content-addressable memory module has a bidirectional match line associated with it. A register's bidirectional match line carries a match signal only if that register contains data matching the pattern bits specified by the mask and the bidirectional match line is receiving a match signal from an external source. Clearing logic associated with each register clears the register when a clear signal appears on the clear line while the register's bidirectional match line is carrying a match signal. In content-addressable memories constructed of such content-addressable memory modules, memory match lines connect match lines associated with a number of registers. The memory match line and all of the match lines connected to it carry match signals only if each of the registers associated with the match lines contains data matching the pattern and mask input to the content-addressable memory module containing the register. The content-addressable memory module further contains logic allowing the use of encoded addresses to address individual registers in the content-addressable memory module.