| 摘要 |
A content-addressable memory (CAM) has an array of four-transistor memory cells arranged in rows corresponding to stored words and columns corresponding to a selected search word. Complementary column lines couple signals associated with the bits of the search word to the memory cells associated with all of the stored words in parallel. The memory cells of each row are coupled to a common sense line and cause a current to flow on the sense line in response to the search word not matching the data word associated with that row. Writing is accomplished by discharging one of the sense lines and applying signals representative of the desired word to be stored to the column lines. Since the ground lines are not unique to any row, they can be shared between adjacent rows or columns as best suits the layout of the circuit. A status bit is associated with each stored word and is used to selectively activate the sense amplifier associated with each row. The status bit is responsive to the signal on sense line and a separate control line, thus, simple comparisons can be used to selectively activate sense amplifiers. Finally, a unique control circuit associated with the most significant bit allows a selected segment of the content-addressable memory to be activated.
|
