Dave's PCF WIP: Paragraphs

Paragraphs

Actions	Matter	Content	Para #	Notes	Modified
View Edit Delete	US10998041B1	Another read scan operation that may be used is referred to as a Bit Error Rate Estimation (BES) method. "Bit error rate" refers to a measure of a number of bits in error of a total overall number of bits processed. Depending on the use case, a bit error rate may be calculated either before, or after, an Error Correction Code (ECC) decoder has made one or more attempts to correct one or more bits in error.	163	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	Like a valley search operation, a BES read scan operation is an iterative trial and error method that seeks to determine an optimal read level for one or more read levels. Similarly, to set read levels for Page 1 504, a BES read scan operation may check read level A 406, read level D 412, read level F 416, and read level K 426. However, a BES read scan operation may be optimized to determine a most likely optimal candidate read level for each read level and as the BES read scan operation tests for one read level, an emulator may determine the results of scanning Page 1 504 with the other read levels set a certain starting levels. In one embodiment, the scanning may be different from reading because threshold voltages determined are emulated and data from memory cells is not actually read, in the normal sense. Use of aspects of the disclosed solution may enable a BES read scan operation to read at the read levels but perform fewer emulated threshold voltage determinations in the scanning part of the BES read scan operation. In this manner, the BES read scan operation seeks to limit a number of iterations of read/sense operations performed on the memory cells to determine optimal read levels.	164	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	BES read scan operations may start with all read levels at a predetermined starting point and take sensed measurements for different candidate read levels for a first read level. For example, a BES-based scan may begin at #4 for read level A 406, then iterate in a predefined order (#3, then #5, then #6, then #2, etc.) through the candidate read levels of read level window 602 while keeping other read levels (read level D 1110, read level F 416, and read level K 1114) in the same position. "Predefined order" refers to a sequence of steps, operations, selections, functions, determination, or actions in an order that is defined before an operation that follows the predefined order is initiated.	165	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	These other read levels may be emulated rather than sensed. When a minimum (fewest number of memory cells activated or fewest number of bit errors) has been indicated among the first set of sets of candidate read levels 610, determining read level A 406, the next set of candidate read levels for a next read level may be analyzed. In certain instances, minimum here relates to a minimum number of check nodes (syndrome weights), which may be used as an estimate of BER based on different hypotheses related to the number of senses performed. To obtain syndrome weights, a BES read scan operation may read and decode data using a decoder, and this process may take significant time.	166	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	When the syndrome weights are below a threshold, the relative value of a syndrome weights is a suitable proxy or indicator for a bit error rate. In this manner, the BES read scan operation leverages an estimated bit error rate. "Estimated bit error rate" refers to a value that directly, indirectly, and/or approximately represents a bit error rate for a certain set of data bits stored in one or more memory cells. Advantageously, an estimated bit error rate serves as a suitable proxy for a calculated bit error rate and may be obtained with fewer computing cycles and in a faster time than time needed to determine a bit error rate.	167	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	One example of an estimated bit error rate is a rate resulting from a Bit Error Rate (BER) Estimation Scan (BES) operation. A BES read scan operation is a type of read scan operation in with candidate read levels for certain read levels for a logical page a tested in a predefined order. In one embodiment, the BES read scan operation tests a particular candidate read level and an algorithm determines results for simulated/emulated testing of other read levels for a particular logical page.	168	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	A BES read scan operation, in one embodiment, may determine an estimated bit error rate by comparing syndrome weights between iterative read level sensing or read operations to determine which candidate read level results in the fewest number of activated memory cells. In such embodiments, a syndrome weight below a threshold serves as a proxy for a bit error rate, an estimated bit error rate. A syndrome weight is a number of unsatisfied ECC parity check equations nodes/equations from a Low-Density Parity-Check (LDPC) error correction code decoder (ECC decoder).	169	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	In a Low-Density Parity-Check (LDPC) ECC decoder, a syndrome weight for a codeword is a number of unresolved equations, or unsatisfied check nodes, when the codeword is decoded. On average, the greater the number of unsatisfied check nodes (higher syndrome weight) the higher the number of errors in the codeword. On average, the fewer the number of unsatisfied check nodes (higher syndrome weight) the lower the number of errors in the codeword. Thus, in certain instances, a codeword with fewer errors may still have a greater the number of unsatisfied check nodes (higher syndrome weight).	170	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	In addition, a BES read scan operation may test candidate read levels in a predefined order. For example, when checking for read level D 412, the predefined order of candidate read levels may be #10, then #13, then #14, then #8, then #9. This predefined order may be determined by a manufacturer based on a series of tests and research and development to understand which candidate read levels are most likely to result in the lowest bit error rate after the fewest number of iterations within the BES read scan operation.	171	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	There are various other aspects to the BES read scan operation which are not discusses in detail here. Instead, suitable implementations of a BES read scan operation for use with aspects of the disclosed solution are described in U.S. Pat. No. 9,697,905 filed Dec. 4, 2014, issued Jul. 4, 2017, which is hereby incorporated by reference for all purposes	172	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	FIG. 7 depicts an example of correlations between memory states 700 and adjustments to read levels for a set of multi-level storage cells of non-volatile memory media. Those of skill in the art recognize that threshold voltages for memory cells change over time due to various factors, including temperature changes, wearing of the memory cells, disturb influences, leakage, and the like. Generally, such changes are not problematic for a majority of the memory cells within a cell threshold voltage distribution. However, these changes in threshold voltage may result in higher bit error rates due to memory cells near the boundaries of the memory states (such boundaries may be referred to a lower tail for a part of the distribution curve closest to the lowest threshold voltages and an upper tail a part of the distribution curve closest to the higher threshold voltages) moving from having a threshold voltage within one memory state to having a threshold voltage within a neighboring memory state (adjacent memory state).	173	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	To address these changes, the read scan operation adjusts the read levels at the cell threshold voltage distribution curve boundaries. FIG. 7 illustrates a few example memory states in which the read level adjustment has been made. Curves illustrated in solid lines represent a current distribution and those illustrated in dashed lines represent what the cell threshold voltage distribution was in the past.	174	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	In the example illustrated, adjustments to create adjusted read level B 702, adjusted read level E 704, and adjusted read level G 706 have been made. The previous read levels are also indicated as previous read level B 708, previous read level E 710, and previous read level G 712. The read scan operation, in one embodiment, determines different adjustments to the previous read levels, resulting in the adjusted read levels. In the depicted embodiment, the read scan operation may determine adjustment 714, adjustment 716, and adjustment 718 individually for the different memory states B, E, and G, with different magnitudes, different directions, and the like, customizing the different adjustment levels, adjusted read level B 702, adjusted read level E 704, and adjusted read level G 706 individually to media characteristics of the different memory states B, E, and G. Each memory state Er, A, B, C, etc., through O as illustrated in FIG. 4 may receive this treatment. A subset of the memory states, Er through G, are illustrated here for convenience.	175	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	The adjusted read levels align with the changed cell threshold voltage distributions. Were previous read levels, such as previous read level B 708, previous read level E 710, previous read level G 712 used, the memory cells near the boundaries would register data errors. Similarly, because the charge levels of the different memory states A, D, and G have drifted, leaked, been disturbed, or the like by different amounts, and/or in different directions, using the same adjustment for each memory state B, E, and G, in certain embodiments, may register data errors. By configuring the corresponding set of storage cells to use the individually adjusted read levels, the read scan operation may prevent, avoid, or correct potential data errors. In one embodiment, the read scan operation determines the adjusted read levels, adjusted read level B 702, adjusted read level E 704, and adjusted read level G 706, reactively, after a bit error rate crosses a threshold. In another embodiment, the read scan operation determines the adjusted read levels proactively based on operating conditions and media characteristics for a corresponding set of memory cells.	176	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	As is illustrated here, an increasing threshold voltage shift 720 of memory state A may necessitate adjustment 714 resulting in an adjusted read level B 702 (wherein read level B demarcates the transition between memory state A and memory state B). Similarly, an increasing threshold voltage shift 720 of memory state D may necessitate adjustment 716 to adjusted read level E 704. A decreasing threshold voltage shift 722 to memory state G, on the other hand, may necessitate adjustment 718 to adjusted read level G 706, based on the illustrated example in FIG. 7.	177	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	One may observe that the increasing threshold voltage shift 720 of memory state A 728 is frequently accompanied by an increasing threshold voltage shift 720 of memory state D 730. These shifts are one example of a correlation. "Correlation" refers to a relation existing between phenomena, attributes, behaviors, or things or between mathematical or statistical variables which tend to vary, be associated, or occur together in a way not expected on the basis of chance alone. ("Correlation." Merriam-Webster.com Dictionary, Merriam-Webster, Accessed 10 Apr. 2020. Edited.)	178	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	A relation/correlation may be represented in a variety of ways, including by use of numbers, formulas, graphs, diagrams or the like. In certain embodiments, the correlation may represent a one-way relationship between a first thing and a second thing, meaning the correlation exists from the first thing to the second thing but not from the second thing to the first thing. In other embodiments, the correlation may represent a two-way relationship between a first thing and a second thing, meaning that the same correlation exists in comparing the first thing to the second thing and from the second thing to the first thing.	179	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	In certain embodiments, the correlation represents a magnitude and/or rate of change in an attribute or behavior between two or more things. Correlations may be observed, or derived, by testing and analysis of results from normal use, experiments, machine learning, or the like. Correlations between two things, such as memory cells, threshold voltages, memory die, memory states, cell threshold voltage distributions, or the like, may be characterized as positive correlations or negative correlations.	180	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	Specifically, because the increasing threshold voltage shift 720 of memory state A occurs in the same direction as the increasing threshold voltage shift 720 of memory state D, the correlation between them is referred to as a positive shift correlation 724. "Positive correlation" refers to a correlation in which two or more correlated things respond in the same manner to a particular influence, environment, action, or stimuli. For example, where threshold voltages of memory cells are represented by cell threshold voltage distributions and the cell threshold voltage distributions are mapped to memory states, memory cells within a first memory state are positively correlated to memory cells within a second memory state when the correlated attribute changes in the same direction for the memory cells of the first memory state and the memory cells of the second memory state.	181	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	Said another way, if the correlated attribute increases for the memory cells of the first memory state and the correlated attribute increases for the memory cells of the second memory state, this is a positive correlation. In certain embodiments, the correlated attribute may comprise a threshold voltage, or change in a cell threshold voltage distribution for a set of memory cells in a memory state.	182	Added by DJM 12 2021	12/22/21, 12:00 AM

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