Research On The Influence Of Don't Care Bits On Decomposing Transform Compression Method

In recent years,with the rapid developrment of electronic industry,intelligent terminal equipment has become an essential part of life.In order to meet the needs of the market,the integrated circuit manufacturing technology is improving,and the number of integrated transistors on the chip is increasing rapidly,which makes the testing of integrated circuits become more and more complicated.The increasing complexity of the chip will increase the probability of failure,thus making the number of faults more and more,and the test data for fault detection will also increase.Increasing the scale of test data not only requires more storage space,but also increases test application time and test power consumption.Therefore,how to effectively reduce the stored test data has become a hot topic in the field of IC testing.In order to reduce the cost of test data storage and shorten test application time,test data can be compressed.Test data compression is designed to reduce the number of binary bits that test data needs to store.The data is compressed and stored on the tester,and the decompression circuit on the chip is responsible for applying the data from the tester to the circuit under test.In this paper,tlhe test excitation compression method is studied,which includes the following two aspects:(1)The influence of don't care bits on the compression ratio of the decomposing transform compression method is studied by using the residual component sharing method.Taking advantage of the potential compatibility between the bitstreams of the original test set,the shared method makes one residual component be used by multiple bit streams when the original test set is divided into principal component set and residual component set,thus reducing the scale of the residual set.For single-run coding,reducing the size of the test set can reduce the length of coded codewords and facilitate compression.The experimental results show that the average sharing degree of the residual component of the bitstream in the test set is 1.74,but the average compression ratio is only 72.54%,which is 2.87%less than the decomposition of the test set using the principle of" least of the residual components".(2)The influence of don't care bits on the compression ratio of the decomposing transform compression method is studied by using the difference vector selectively.The method reduces the number of runs in the test set by the selective differential processing of the test vector.The specific method is to fill the irrelevant bits in the test set according to the "follow" strategy,and then fill each bit of data in the vector to obtain the difference vector,and compare the number of runs between the original test vector and the difference vector.The vector with fewer runs is retained,which forms a combined test set and encodes and compresses the combination test set.The experimental results show that the average compression ratio of the original test set is 59.78%,which is slightly higher than that of the direct coding compression of the test set.The results show that reducing the size of the test set by using don't care bit priority has no positive effect on the compression rate of the decomposing transform compression method.Conversely,priority should be given to reducing the number of runs.