Patent ID: 6809945
Filing Date: 2004-10-26
Classification: G11C

Abstract:
In a content addressable memory comprising a group of content addressable cells and a group of corresponding match switches coupled by a first match sense line, each match switch being switchable to a first state in the event of a match between data stored in a corresponding cell and test data and being switchable to a second state in the event of a mismatch between data in the corresponding cell and the test data, the first sense match line being switched to a first voltage in the event all of the match switches in the group are in the first state and being switched to a second range of voltages in the event one or more of the match switches in the group are in the second state, apparatus for detecting the state of the first match sense line comprising:a second match sense line different from the first match sense line; a second switch outside the group of corresponding match switches coupled to the second match sense line; a third switch outside the group of corresponding match switches coupled in series with the second switch; and a differential amplifier coupled to the first match sense line and the second match sense line arranged to detect the difference in voltage between the first match sense line and the second match sense line.