Encoding Test Pattern of System-on-Chip (SOC) Using Annular Scan Chain

With the improvement of System-on-Chip integration, the chip requires an increasingly large amount of test data. To solve the contradiction between the storage capacity and bandwidth of automatic test equipment (ATE), a new method of test data compression/decompression is proposed based on an annular scan chain. Corresponding fault bits of different test patterns are incompatible, moving test patterns in an annular scan chain, makes all of the new corresponding bits of different test patterns be compatible or backward-compatible, so different adjacent test patterns form a new relation that are indirectly compatible or indirectly backward-compatible, achieves the purpose of test data compression by encoding these indirectly compatible test patterns or indirectly backward-compatible test patterns. According to experimental results, the average compression ratio increases by %6.94 to % 15.1 compared with the other schemes, relative decompression architecture is simple. In the annular scan chain, the test pattern moves clockwise with the minimal bits, generating subsequent test patterns quickly, it is advantageous to reduce the test application time of a single IP core.