A Method to Detect Bit Flips in a Soft-Error Resilient TCAM

Ternary content addressable memories (TCAMs) are special memories which are widely used in high-speed network applications such as routers, firewalls, and network address translators. In high-reliability network applications such as aerospace and defense systems, soft-error tolerant TCAMs are indispensable to prevent data corruption or faults caused by radiation. This paper shows a novel way in generating keys to cover the correct match. It proposes a novel soft-error tolerant TCAM for multiple-bit-flip errors using partial don't-care keys (X-keys). First, this paper observes the case of single-bit-flip errors by X-TCAM. Second, it extends the X-TCAM to the case of multiple-bit-flip errors called KX-TCAM, where K stands for the maximum number of errors k. KX-TCAM corrects up to k-bit-flip errors and enhances the tolerance of the TCAM against soft errors, where k is the maximum number of bit flips in a word of a TCAM. KX-TCAM consists of a TCAM, a preprocessed don't-care-bit index look-up memory (X look-up), and a backup error checking and correction (ECC)-SRAM. First, KX-TCAM randomly selects a search key. After that, KX-TCAM detects multiple-bit-flip errors by the generated X-keys using the X look-up. If the keys match the different locations, then a soft error is suspected and KX-TCAM refreshes the TCAM words by using the backup ECC-SRAM. Experimental results show that the soft-error tolerance capability of KX-TCAM significantly outperforms existing state-of-the-art schemes. Moreover, the hardware overhead of KX-TCAM is small due to the use of a single TCAM. KX-TCAM can be easily implemented and is useful for fault-tolerant packet classifiers.