Device and method for ensuring current consumption in search engine system
View Patent ↗A search engine system ( 100 ) can include a key multiplexer ( 104 ) and logic circuit ( 108 ). A key from a previous operation can be received by logic circuit ( 108 ) and altered to generate an idle key. In a non-search operation, the idle key can be applied to a CAM section to draw current as in a normal search operation. Logic circuit ( 108 ) can ensure that an idle key value is always different than a previously applied key value.
1. A search engine system, comprising:
at least one content addressable memory (CAM) section that draws current in response to an applied key value;
a logic circuit that changes at least a portion of the applied key value to generate an idle key value; and
a selection circuit for selectively providing a key value associated with a search operation or the idle key value as the applied key value.
2. The search engine system of claim 1 , wherein:
the logic circuit changes all the bits of the applied key value to generate the idle key value.
3. The search engine system of claim 1 , wherein:
the logic circuit selectively changes bits of the applied key value to generate the idle key value.
4. The search engine system of claim 1 , further including:
the selection circuit comprises a key multiplexer (MUX) having one input coupled to receive a key value associated with a search operation, another input coupled to the logic circuit, and an output coupled to the CAM section.
5. The search engine system of claim 1 , further including:
a register for storing the idle key output from the logic circuit.
6. The search engine system of claim 3 , wherein:
logic circuit selectively changes bits of the applied key value in response to at least one control signal.
7. The search engine system of claim 5 , further including:
a feedback path coupled between the key MUX output and the logic circuit.
8. A search engine system current control method, comprising the steps of:
in a search operation, providing a key value corresponding to the search operation to a CAM section; and
in an idle operation, providing an internally generated key value that varies from a key value provided in a previous operation to the CAM section.
9. The method of claim 8 , wherein:
the internally generated key value is generated by changing the key value provided in the previous operation.
10. The method of claim 9 , wherein:
changing the key value provided in the previous operation includes complementing the bit values of at least a portion of the key value provided in the previous operation.
11. The method of claim 9 , wherein:
changing the key value provided in the previous operation includes changing all the bit values of the key value provided in the previous operation.
12. The method of claim 9 , wherein:
changing the key value provided in the previous operation includes changing less than all the bit values of the key provided in the previous operation.
13. The method of claim 9 , wherein:
changing the key value provided in the previous operation includes dynamically changing bit values of the key value provided In the previous operation in response to at least one control signal.
14. The method of claim 13 , wherein:
dynamically changing bit values includes providing one control signal that controls the changing of one bit value.
15. The method of claim 13 , wherein:
dynamically changing bit values includes providing one control signal that controls the changing of a plurality of bit values.
16. A search engine system, comprising:
an applied key bus that provides an applied key value to at least one search engine section; and
at least one logic circuit having an input coupled to the applied key bus that alters at least a portion of the applied key value to generate an idle key value that is applied to the at least one search engine section in a non-search operation.
17. The search engine system of claim 16 , further including:
a key multiplexer (MUX) having a first input coupled to receive a search key value generated in response to a search operation, a second input coupled to the logic circuit to receive the idle key value, and an output coupled to the applied key bus.
18. The search engine system of claim 16 , further including:
a register that stores a key value having an output coupled to the at least one search engine section.
19. The search engine system of claim 16 , wherein:
the at least one search engine section includes a plurality of separately searchable CAM sections, each including a plurality of CAM entries; and
the at least one logic circuit includes a logic circuit corresponding to each CAM section that provides an idle key value to the corresponding CAM section.
20. The search engine system of claim 16 , wherein:
the at least one search engine section includes a plurality of separately searchable CAM sections, each including a plurality of CAM entries; and
the at least one logic circuit includes a logic circuit that provides an idle key value to the plurality of CAM sections.