Patent ID: 9620246
Date: 2017-04-11
CPC Classifications: G06F,G11C

Claim:
1. A read method of a semiconductor memory system including a nonvolatile memory device and a memory controller, the read method comprising: a first step of performing a first ECC decoding to first data stored in the nonvolatile memory device, wherein the first data is read using a first read voltage; a second step of generating second data by re-reading the first data using a second read voltage when the first ECC decoding fails; a third step of generating third data by performing a second ECC decoding to the second data; a fourth step of obtaining an error-bit-number, which is a number of bits different between the second data and the third data, when the second ECC decoding fails; a fifth step of repeating the second to fourth steps by changing the second read voltage until the error-bit-number is smaller than a predetermined threshold value; and a sixth step of performing a third ECC decoding to an optimal data.