METHOD AND DEVICE FOR COMPRESSING AND EXPANDING DATA PATTERN

摘要

PURPOSE: A test pattern compressing method and a test pattern expanding method are provided to apply an optimum compressing method to a data pattern having portions each of which has a different structure or a different statistical characteristic; be reconstructed to the original data pattern from the respective blocks without any information loss. CONSTITUTION: The dividing step includes the step of: calculating a threshold value of entropy for dividing the input data into blocks; measuring an appearing probability of each symbol in the input data to calculate a data entropy from the appearing probabilities of symbols; comparing an actual data entropy with the threshold value; and distributing a divided data portion to one of the plurality of blocks in accordance with the comparison result. The dividing step for expanding the compressed data is characterized in that the compressed data is divided into data compressed by the run length compressing method and data compressed by the other plurality of compressing methods and the divided data compressed by the run length compressing method are expanded by a run length expanding method in the step of applying the appropriate expanding method. The test pattern compressing apparatus comprises dividing means for dividing an inputted test pattern into test sequences each corresponding to a pin of an integrated circuit under test, and test sequence compressing means for selecting an appropriate compressing method in accordance with a data structure of each test sequence to compress the test sequence for each pin.