Granted Patent B2

US 7,581,059 · App. 11/460,615 · Granted Aug 25, 2009

Abstract

Claims (36)

1. A content addressable memory (CAM) device comprising:

a CAM array to store data values in entries having respective addresses and to compare the data values with a search key;

an interface to receive a first address and a second address that define a range of the addresses;

range-control circuitry to generate a hit signal having either a first state or a second state according to whether any of the entries having addresses within the range of addresses match the search key;

wherein the range-control circuitry includes:

a decoder circuit to receive the first address and a plurality of match signals, and to output a plurality of enable signals each having either a first state or a second state according to the state of each corresponding match signal and whether their respective addresses are greater than or equal to the first address; and

an encoder circuit to receive the plurality of enable signals and to output a match address and an intermediate result signal.

2. The CAM device of claim 1 wherein the interface comprises a first address input and a second address input to enable the first and second addresses to be received concurrently.

3. The CAM device of claim 1 wherein the interface comprises a time-multiplexed input to receive the first and second addresses sequentially.

4. The CAM device of claim 1 wherein the second address is greater in numerical value than the first address.

5. The CAM device of claim 4 wherein the second address is lower in numerical value than a last address of the CAM array.

6. The CAM device of claim 4 wherein the CAM array comprises the plurality of match signals each corresponding to a row of CAM cells, each match signal having either a first state or a second state according to whether contents within the respective row matches the search key.

7. The CAM device of claim 1 further comprising an end-compare circuit, wherein the end-compare circuitry comprises:

a comparator to receive the second address and the match address, and to output a comparator result signal having either the first state or the second state according to whether the match address is greater than or equal to the second address; and

a logic gate to receive the comparator result signal and the intermediate result signal, and to output the hit signal.

8. A content addressable memory (CAM) device comprising:

a CAM array to store data values in entries having respective addresses and to compare the data values with a search key;

an interface to receive a first address and a second address that define a range of the addresses;

range-control circuitry to generate a hit signal having either a first state or a second state according to whether any of the entries having addresses within the range of address match the search key;

wherein the range-control circuitry includes:

a decoder circuit to receive the first address, the second address, and the plurality of match signals, and to output a plurality of enable signals each having either a first state or a second state according to the state of each of corresponding match signal and whether the numerical values of their respective addresses are greater than or equal to that of the first address and less than or equal to that of the second address; and

an encoder circuit to receive the plurality of enable signals and to output a match address and the hit signal.

9. Computer-readable media having information embodied therein that includes a description of an integrated circuit device, the information including descriptions of:

a CAM array to store data values in entries having respective addresses and to compare the data values with a search key;

an interface to receive a first address and a second address that define a range of the addresses;

range-control circuitry to generate a hit signal having either a first state or a second state according to whether any of the entries having addresses within the range of addresses match the search key; and

wherein the range-control circuitry includes:

a decoder circuit to receive the first address and the plurality of match signals, and to output a plurality of enable signals each having either a first state or a second state according to the state of each corresponding match signal and whether their respective addresses are greater than or equal to the first address; and

an encoder circuit to receive the plurality of enable signals and to output a match address and an intermediate result signal.

10. Computer-readable media having information embodied therein that includes a description of an integrated circuit device, the information including descriptions of:

a CAM array to store data values in entries having respective addresses and to compare the data values with a search key;

an interface to receive a first address and a second address that define a range of the addresses;

range-control circuitry to generate a hit signal having either a first state or a second state according to whether any of the entries having addresses within the range of addresses match the search key;

wherein the range-control circuitry includes:

a decoder circuit to receive the first address, the second address, and the plurality of match signals, and to output a plurality of enable signals each having either a first state or a second state according to the state of each of corresponding match signal and whether the numerical values of their respective addresses are greater than or equal to that of the first address and less than or equal to that of the second address; and

an encoder circuit to receive the plurality of enable signals and to output a match address and the hit signal.

Assignments (10)