An almost full flag is asserted when all but one of the rows of a CAM array contain valid data, as indicated by corresponding valid bits. In one embodiment, the almost full flag is generating using match logic and multiple match logic, where the match logic asserts a first signal when at least one of the CAM rows contains invalid data, and the multiple match logic asserts a second signal when more than one CAM row contains invalid data. The almost full flag is asserted when the first asserting is asserted indicating there is at least one available row and the second signal is de-asserted indicating there is no more than one available row. Thus, when asserted, the almost full flag indicates that there is only one available CAM row. Subsequent instructions are monitored to detect an instruction which calls for writing valid data to the one available CAM row. The full flag is asserted when such an instruction is detected while the almost full flag is asserted.
A signal detection circuit detects the presence or absence of signals having the same logic in a plurality of arranged signal lines, can be used as a circuit suitable for multi-hit detection in a content addressable memory. The signal detection circuit includes a first signal transmission line to transmit a first signal indicating the presence of two or more logical signals to be detected and a second signal transmission line to transmit a second signal indicating the presence of one or more of the logic signals to be detected. Each of the first and second signal transmission lines includes logic circuits. The signal detection circuit may have a hierarchical structure.
A CAM array which enables a learning process to be an extension of a search process is disclosed. When a search fails to find a matching data in the CAM array, the searched data can automatically be written to a next free address without resorting to any additional search or selection processes.
A CAM array which enables a learning process to be an extension of a search process is disclosed. When a search fails to find a matching data in the CAM array, the searched data can automatically be written to a next free address without resorting to any additional search or selection processes.
The configuration of a CAM device can be set in various manners depending on a system in which CAM having different configurations is needed. The CAM device includes a CAM array including a plurality of physical banks, a logical bank-physical bank converter for setting the assignment between logical banks and physical banks, and for outputting a control signal to set the configuration of a physical bank assigned to the logical bank, depending on a logical bank signal indicating a logical bank to be searched, a priority circuit for outputting search results in accordance with predetermined priority, and a cascade circuit for performing a logical operation on the search results output from the priority circuit of the present CAM device and a search results supplied from a higher-order CAM device, and transmitting the results of the logical operation to a lower-order CAM device.
A search engine method and apparatus can store and update status information for each entry of a content addressable memory (CAM) array, for a learn operation, or the like. A search engine can include a status memory block external to and independent of the CAM array. A status memory block (800) can include a number of memory sections (806-0 to 806-2) that each includes a number of bit locations for storing a free/not-free status of CAM entries in a hierarchical fashion. Corresponding control sections (808-0 to 808-2) can include priority encoders (812-0 to 812-2) that determine a first free element in a memory section for a next hierarchical level, as well as status aggregation logic (814-0 to 814-2) that can generate an aggregated status that is propagated to a previous hierarchical level.
