A test apparatus includes a test section that executes testing of each cell of the memory under test, a fail information storage section that stores fail information in a fail memory; a counting section that counts the number of defective cells in each block, a reading request receiving section that receives a request to read the fail information of each cell, a comparing section that compares the number of defective cells in a block to a predetermined reference number, a converting section that, in a case where the number of defective cells exceeds the predetermined reference value, converts a plurality of consecutive pieces of fail information in a response data string into a value indicating defectiveness, and a compressing section that compresses the response data string and returns a compressed response data string.
1. A test apparatus that tests a memory under test, comprising:
a test section that executes testing of each cell of the memory under test;
a fail information storage section that stores fail information corresponding to each cell of the memory under test that indicates pass/fail of the cell in a fail memory;
a counting section that counts a number of defective cells detected in each block for every block in the memory under test, a block being a unit that can be replaced with a backup storage region when a defect occurs;
a reading request receiving section that receives a reading request to read the fail information corresponding to each cell included in a reading target block;
a comparing section that compares the number of defective cells in the reading target block to a predetermined reference number and outputs a comparison result;
a converting section that receives the read fail information and the comparison result and outputs modified fail information, of the same size as the read fail information, in which, in a case where the number of defective cells in the reading target block exceeds the predetermined reference number, one or more pieces of fail information indicating pass among the read fail information are converted into fail information indicating fail; and
a compressing section that compresses the modified fail information and returns the compressed fail information.
2. The test apparatus according to claim 1 , wherein the converting section, in a case where the number of defective cells in the reading target block exceeds the predetermined reference number, outputs modified fail information that indicates that all of the cells in the reading target block are defective.
3. The test apparatus according to claim 2 , wherein the compressing section, in a case where the modified fail information includes a plurality of consecutive pieces of fail information having the same value, executes a run length compression that replaces the plurality of consecutive pieces of fail information with information that indicates the value of the plurality of consecutive pieces of fail information and the number of consecutive pieces of fail information.
4. The test apparatus according to claim 1 , further comprising a block information storage section that stores, corresponding to each block in the memory under test, block defect information that indicates whether defective cells exist in a block and defect excess information that indicates whether the number of defective cells in the block exceeds the predetermined reference number wherein
the converting section, in a case where the defect excess information indicates that the number of defective cells in the reading target block exceeds the reference number, outputs modified fail information that indicates that all of the cells in the reading target block are defective.
5. The test apparatus according to claim 1 , wherein the converting section, in a case where the number of defective cells in the reading target block does not exceed the predetermined reference number, outputs modified fail information that is the same as the read fail information.