Nonvolatile memory system with background reference positioning and local reference positioning
First Claim
1. A method for reducing latency of a nonvolatile memory controller comprising:
- identifying a plurality of page groups in each block of a nonvolatile memory device;
performing a background read of an indicator page of each block of the nonvolatile memory device at a predetermined timing interval;
determining the number of errors in the background read of the indicator page of each block;
identifying a block having a determined number of errors exceeding an error threshold as an outlier block;
performing background reads of representative pages of each page group of the outlier block at offsets to each threshold voltage that is required for reading the representative pages of each page group of the outlier block to identify a set of updated threshold voltage offset values for each page group of the outlier block;
upon the occurrence of one or more of an endurance event, a retention timer event and a read disturb event at a closed block, performing background reads of representative pages of each page group of the closed block at offsets to each threshold voltage that is required for reading the representative pages of each page group of the closed block to identify a set of updated threshold voltage offset values for each page group of the closed block; and
when a usage characteristic is determined to meet one or more usage characteristic threshold, performing subsequent host-requested reads of pages of each block meeting the one or more usage characteristic threshold using a threshold voltage shift read instruction and using the set of updated threshold voltage offset values corresponding to the page group of the page being read.
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Abstract
A nonvolatile memory system, a nonvolatile memory controller and a method for reducing latency of a memory controller are disclosed. The nonvolatile memory system includes a read circuit that performs background reads of an indicator page of each block to identify outlier blocks. A background reference positioning circuit performs background reads of representative pages of the outlier block at threshold voltage offsets to identify sets of updated threshold voltage offset values. Upon endurance events, retention timer events and read disturb events at a closed block background reads are performed of representative pages of the closed block at threshold voltage offsets to identify sets of updated threshold voltage offset values. When a usage characteristic meets one or more usage characteristic threshold, the read circuit performs subsequent host-requested reads of pages of blocks meeting the usage characteristic threshold using a threshold voltage shift read instruction and using the corresponding set of updated threshold voltage offset values.
291 Citations
20 Claims
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1. A method for reducing latency of a nonvolatile memory controller comprising:
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identifying a plurality of page groups in each block of a nonvolatile memory device; performing a background read of an indicator page of each block of the nonvolatile memory device at a predetermined timing interval; determining the number of errors in the background read of the indicator page of each block; identifying a block having a determined number of errors exceeding an error threshold as an outlier block; performing background reads of representative pages of each page group of the outlier block at offsets to each threshold voltage that is required for reading the representative pages of each page group of the outlier block to identify a set of updated threshold voltage offset values for each page group of the outlier block; upon the occurrence of one or more of an endurance event, a retention timer event and a read disturb event at a closed block, performing background reads of representative pages of each page group of the closed block at offsets to each threshold voltage that is required for reading the representative pages of each page group of the closed block to identify a set of updated threshold voltage offset values for each page group of the closed block; and when a usage characteristic is determined to meet one or more usage characteristic threshold, performing subsequent host-requested reads of pages of each block meeting the one or more usage characteristic threshold using a threshold voltage shift read instruction and using the set of updated threshold voltage offset values corresponding to the page group of the page being read. - View Dependent Claims (2, 3, 4, 5)
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6. A nonvolatile memory controller comprising:
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a status circuit configured to determine a usage characteristic of a nonvolatile memory device that includes a plurality of blocks, each block including a plurality of page groups; and a read circuit coupled to the status circuit and configured to perform a background read of an indicator page of each block of the nonvolatile memory device at a predetermined timing interval to identify outlier blocks, wherein a block is identified as outlier block when the number of errors in the background read of an indicator page of the block exceeds an error threshold; a background reference positioning circuit coupled to the read circuit, the background reference positioning circuit configured to perform background reads of representative pages of each page group of the outlier block at offsets to each threshold voltage that is required for reading the representative pages of the outlier block to identify a set of updated threshold voltage offset values for each page group of the outlier block, and upon the occurrence of one or more of an endurance event, a retention timer event and a read disturb event at a closed block the read circuit is further configured to perform background reads of representative pages of each page group of the closed block at offsets to each threshold voltage that is required for reading the representative pages of each page group of the closed block to identify a set of updated threshold voltage offset values for each page group of the closed block; and wherein the read circuit is configured to determine whether a usage characteristic meets one or more usage characteristic threshold and, when the usage characteristic is determined to meet the one or more usage characteristic threshold, the read circuit is configured to perform subsequent host-requested reads of pages of each block meeting the one or more usage characteristic threshold using a threshold voltage shift read instruction and using the set of updated threshold voltage offset values corresponding to the page group of the page being read. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A nonvolatile memory system comprising:
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a plurality of nonvolatile memory devices that each include a plurality of blocks, each block including a plurality of page groups; a memory controller coupled to each of the nonvolatile memory devices, the memory controller configured to perform program operations and read operations on memory cells of the nonvolatile memory devices, the nonvolatile memory controller comprising; a status circuit configured to determine a usage characteristic of a nonvolatile memory device; and a read circuit coupled to the status circuit and configured to perform a background read of an indicator page of each block of the nonvolatile memory device at a predetermined timing interval to identify outlier blocks, wherein a block is identified as outlier block when the number of errors in the background read of the indicator page exceeds an error threshold; a background reference positioning circuit coupled to the read circuit, the background reference positioning circuit configured to perform background reads of representative pages of each page group of the outlier block at offsets to each threshold voltage that is required for reading the representative pages of the outlier block to identify a set of updated threshold voltage offset values for the outlier block, and upon the occurrence of one or more of an endurance event, a retention timer event and a read disturb event at a closed block the read circuit is further configured to perform background reads of representative pages of each page group of the closed block at offsets to each threshold voltage that is required for reading the representative pages of each page group of the closed block to identify a set of updated threshold voltage offset values for each page group of the closed block; and wherein the read circuit is configured to determine whether a usage characteristic meets one or more usage characteristic threshold and, when the usage characteristic is determined to meet the one or more usage characteristic threshold, the read circuit is configured to perform subsequent host-requested reads of pages of each block meeting the one or more usage characteristic threshold using a threshold voltage shift read instruction and using the set of updated threshold voltage offset values corresponding to the page group of the page being read. - View Dependent Claims (17, 18, 19, 20)
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Specification