| CPC G06F 11/076 (2013.01) [G01K 3/005 (2013.01); G06F 3/0619 (2013.01); G06F 3/0659 (2013.01); G06F 3/0679 (2013.01); G06F 11/0727 (2013.01); G06F 11/3058 (2013.01); G11C 16/0483 (2013.01); G11C 16/10 (2013.01); G11C 16/26 (2013.01)] | 20 Claims |

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1. An operation method of a storage device including a nonvolatile memory device, the operation method comprising:
receiving a retention mode activation request including a retention level;
issuing a retention mode command indicating the retention level in response to the retention mode activation request; and
performing a retention operation based on the retention level in response to the retention mode command, wherein a threshold voltage distribution width of valid data written to the nonvolatile memory device in the retention operation corresponds to the retention level.
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