Ternary content addressable memory (TCAM) cells with low signal line numbers

• US 7,570,503 B1
• Filed: 05/22/2006
• Issued: 08/04/2009
• Est. Priority Date: 05/20/2005
• Status: Expired due to Fees

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Netlogic Microsystems Incorporated (Broadcom, Inc.)
• Inventors: Wright, Andrew, Jiang, Bin, Maheshwari, Dinesh, Banachowicz, Bartosz
• Primary Examiner(s): Nguyen; VanThu
• Assistant Examiner(s): Yang; Han
• Application Number:
  US11/438,185
• Time in Patent Office: 1,170 Days
• Field of Search: 365/168, 365/196, 365/207, 365/49.1, 365/68, 365/154
• US Class Current: 365/49.1
• CPC Class Codes: G11C 15/04 using semiconductor elements

Abstract

A ternary content addressable memory (TCAM) cell circuit formed in a TCAM memory cell array having cells arranged in rows and columns can include a first storage circuit with first and second data path, a second storage circuit with a third and fourth data path, and a compare circuit. No more than four conductive lines in a column wise direction have a direct electrical connection to the TCAM cell. Such conductive lines can include a first bit line coupled to the first data path and the third data path and a second bit line coupled to the second data path and the fourth data path.

Claims

1. A ternary content addressable memory (TCAM) cell circuit formed in a TCAM memory cell array having cells arranged in rows and columns, comprising:

a first storage circuit that stores a first data value and has a first data path coupled to a first storage node and a second data path coupled to a second storage node, the first data path and second data path are commonly coupled to a first word line;

a second storage circuit that stores a second data value and has a third data path coupled to a third storage node and a fourth data path coupled to a fourth storage node, the third data path and fourth data path are commonly coupled to a second word line;

a compare circuit that generates a match result at a match node based on the first data value, second data value, and a compare data value; and

no more than five conductive lines disposed in the column wise direction having a direct electrical connection to the TCAM cell for providing non-power supply signals, including a first bit line coupled to the first data path, a second bit line coupled to the third data path, and a third bit line coupled to the second and fourth data paths.

2. The TCAM cell circuit of claim 1, wherein:

the no more than five conductive lines further includes a first compare data line coupled to receive the compare data value and a second compare data line coupled to receive a complementary compare data value.

3. The TCAM cell circuit of claim 1, wherein:

the compare circuit includes

a first charge transfer path comprising a first compare transistor having a control terminal coupled to receive the first data value, and a second compare transistor having a controllable current path in series with the first compare transistor and a gate coupled to receive the compare data value, and

a second charge transfer path electrically in parallel with the first charge transfer path and comprising a third compare transistor having a control terminal coupled to receive the second data value, and a fourth compare transistor having a controllable current path in series with the third transistor and a gate coupled to receive the complementary compare data value.

4. The TCAM cell circuit of claim 1, wherein:

the first, second, third and fourth data paths each consist of one insulated gate field effect transistor.

5. A ternary content addressable memory (TCAM) cell circuit formed in a TCAM memory cell array having cells arranged in rows and columns, comprising:

a first storage circuit that stores a first data value and has a first data path coupled to a first storage node and a second data path coupled to a second storage node;

a second storage circuit that stores a second data value and has a third data path coupled to a third storage node and a fourth data path coupled to a fourth storage node;

a compare circuit that generates a match result at a match node based on the first data value, second data value, and a compare data value; and

no more than five conductive lines disposed in the column wise direction having a direct electrical connection to the TCAM cell for providing non-power supply signals, including a first bit line coupled to the first data path, a second bit line coupled to the third data path, and a third bit line coupled to the second and fourth data paths, wherein

the no more than five conductive lines consists of three conductive lines, the first bit line being further coupled to the compare circuit, and the second bit line being further coupled to the compare circuit.

6. The TCAM cell circuit of claim 5, wherein:

the first data path and third data path are commonly coupled to a first word line; and

the second data path and fourth data path are commonly coupled to a second word line.