Method of Error Detection in a Ternary Content Addressable Memory

A method for error detection in a ternary content addressable memory, TCAM, preferably in real-time, wherein the error detection is initiated with a read operation at a specified input address (200), an additional random access memory, RAM, is provided, wherein said RAM has the same number of locations as the TCAM, wherein in both memories, TCAM and RAM, corresponding read data entries (210) which each consist of data and a mask are placed at the same address locations, and wherein:

• data and mask read operations from TCAM and RAM at the locations pointed by the input address (200) are performed and
• in a first check phase (220) said data and mask read from the TCAM at the location pointed by the input address (200) are compared with the data and mask read from RAM at the location pointed by the same input address (200), and
• if the result of the first check phase (220) is correct, a TCAM_SEARCH phase (270) is executed,
• otherwise a data recovery check (230) is executed, which is followed by a data refresh (240), a second read of data entries (250) stored at said input address (200) in both TCAM and RAM, and a second check phase (260) is executed, in which second phase (260) a comparison of data and masks read from both TCAM and RAM is performed, and
• and wherein the TCAM_SEARCH phase (270) uses the data read from RAM as input search key and returns as an output a TCAM match vector and/or a single TCAM address,
• and wherein a TCAM match check (280) checks
• in the case of a TCAM match vector, whether the result of the TCAM_SEARCH (270), that is a flag pointed by the address (200) from TCAM match vector (275), is binary 1, or
• in the case of a non-matched (false) TCAM single address (300) checked in a TCAM address check (310),
• and if the TCAM address (300) is a lower address than said input address (200), a TCAM read at said TCAM address (300) is performed, and if in a TCAM search validation (340) the TCAM data read at the TCAM address (300) is identical to the data read at the RAM, and wherein preferably the method moves to the next input address (286) provided by the scrubbing mechanism, and the whole proposed error detection method may be repeated.