US 9,852,807 B1Granted

Content addressable memory in an emulation system

AssigneeCadence Design Systems, Inc.

InventorBeshara Elmufdi

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Abstract

Disclosed herein are components of an emulation system capable of efficiently recreating the functionality a CAM/TCAM memory circuit. Rather than using specialized gates or the existing processors, the embodiments described herein configure/instruct the existing memory circuits of the emulation system to imitate a search engine function that queries the existing RAM circuits, portions of which are reconfigured to function as CAM/TCAM memory. The hardware-based search engine and the repurposed memory (e.g., RAM, SRAM, DRAM) allow an emulation system to emulate the functionality of a CAM/TCAM memory. This can be implemented at a low processing cost to the emulation system, as it provides the ability to store more CAM/TCAM data at a very low cost. It can also use the existing system and emulation buses that other components (e.g., processors) of the system use to communicate with the memory, so expansion of the emulation system may not be required.

Claims20

Dependent claims

A memory controller circuit of an emulation system configured to execute read and write commands associated with memories of the emulation system, the memory controller comprising:

a memory block of the emulation system, the memory block comprising:
one or more memories configured to store one or more data bits at memory addresses in the one or more memories;
and
a comparator logic circuit coupled directly to the one or more memories and a first register configured to store a set of pattern bits, the comparator logic circuit configured to generate a set of one or more output bits based upon comparing at least a portion of the set of pattern bits received from the first register and a set of one or more data bits read from one or more of the one or more memories, in accordance with a query-type instruction such that the memory block is configured to emulate a content addressable memory (CAM) or ternary content addressable memory (TCAM) within the emulation system;
and
a test block of the emulation system, the test block comprising one or more circuits, including state machine circuit configured to, upon receiving a query instruction signal, transmit a special read instruction signal to the memory block, the special read instruction comprising the query-type instruction, the set of pattern bits to be stored into the first register, and a set of one or more memory addresses of the one or more data bits to be read into the comparator logic circuit,
wherein the special read instruction further comprises an indication to the memory block that a CAM or TCAM query will begin and a parameter indicating an execution mode of the CAM or TCAM query.

4 more elements

A set of memory block circuits of a memory controller circuit of an emulation system configured to execute read and write commands associated with memories of the emulation system, the memory block circuits comprising:

a first register configured to store a set of one or more pattern bits representing a query;
a comparator logic circuit configured to generate a set of one or more output bits representing a response to the query, the one or more output bits based upon comparing at least a portion of the set of pattern bits from the first register against a set of one or more data bits read from at least one memory of one or more memories, in accordance with a query-type instruction indicating a type of query such that the memory block circuits are configured to emulate a content addressable memory (CAM) or ternary content addressable memory (TCAM) within the emulation system;
and
a state machine controller configured to store the one or more pattern bits into the first register, transmit a special read instruction to the one or more memories instructing the at least one memory to send the one or more data bits to the comparator logic circuit, and to transmit to the comparator logic circuit the query-type instruction indicating the type of query, wherein the special read instruction comprises an indication to the one or more memories that a CAM or TCAM query will begin and a parameter indicating an execution mode of the CAM or TCAM query.

1 more element

A method for emulating CAM and TCAM query functionality using memory control circuits of an emulation system configured to execute read and write commands associated with memories of the emulation system, the method comprising:

upon a memory control circuit receiving a query instruction indicating one or more memory addresses of one or more memories of the memory control circuit, a set of pattern bits modeling a query, and a query-type indicator:
transmitting, by the memory control circuit, a special read instruction signal to the one or more memories, wherein the special read instruction comprises a query-type instruction, an indication that a CAM or TCAM query will begin, and a parameter indicating an execution mode of the CAM or TCAM query;
storing, by the memory control circuit, the set of pattern bits into a first register of the memory control circuit, wherein the first register is coupled to a comparator circuit of the memory control circuit;
transmitting, by the memory control circuit, into the comparator circuit a set of data bits stored in at least one memory of the one or more memories at the one or more addresses;
and
generating, by the comparator circuit of the memory control circuit, a set of one or more output bits based upon comparing the set of data bits from the memory addresses against the set of pattern bits in accordance with the query-type indicator.

3 more elements

Dependencies are inferred from the claim text.