The Research Of SoC Test Data Compression Based On Coding And Inverted Folding

System-on-a-Chip, which is based on IP cores reusing technology, is a representative product of VDSM and nanometer times. SoC has incomparable advantages not only in developing period, but also in the system function and performance. However, with the increase of the amount of IP cores integrated, the chip's complexity and test data volume grow persistently. Meanwhile, Auto Test Equipment becomes more and more expensive, which leads to speedy increase of test cost and difficulty. This problem is drawing more and more attention. A direct and effective solution is to compress the test set, thereby the test cost will be reduced because of decreased volume of SoC test data.Two schemes are proposed in this thesis to compress the test data of SoCs, and the main work is as follows:(1) Prevalent SoC test methods are classified as: BOST, BIST, and Hybrid Self Test. By way of illustration, their principles are analyzed and their fetures are presented.(2) The first scheme is described, which is called Improved Frequency-Directed Run-Length (IFDR) code. In FDR, only run-lengths of 0s are compressed by coding while run-lengths of 1s lavish 2 bits on every 1. To solve this problem, IFDR codes both run-lengths of 0s and run-lengths of 1s, and it achieves higher compression ratio. IFDR also presents a better way to determine don't-care bits. IFDR belongs to BOST.(3) The second scheme, which is called New Converse Folding Scheme (NCFS), is based on folding counter technology. A new folding circuit is designed and the converse folding relationship between test patterns are mended, so NCFS can records the whole test set by one seed and some folding distances between patterns. Because of its character, we don't need to divide scan chains into odd ones and even ones, to say nothing of adding a don't-care bit to a pattern when the length of scan chain is odd. It is simple and flexible to calculate the folding distances and to choose which way to go. Moreover, NCFS's circuit is simpler than former schemes, and it economizes hardware more. NCFS belongs to Hybrid Self Test.Experimental results for the ISCAS 89 benchmark circuits show that these 2 schemes can achieve high compression ratio and restore the original data, so they are very effective compression methods.