Dave's PCF WIP: Paragraphs

Paragraphs

Actions	Application	Content	Paragraph Number	Notes	Modified
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View Edit Delete	US10998041B1	FIG. 9 and FIG. 10 illustrate a shift correlation table 900 and a width correlation table 1000, respectively. One embodiment may use one of or both a shift correlation table 900 and a width correlation table 1000 or a table that combines correlation factors from both. In one embodiment, shift correlation table 900 and width correlation table 1000 store correlation factors which are used to improves read scan operations. Shift correlation table 900 and width correlation table 1000 are but examples of a variety of possible types of correlation data structures that embodiments of the claimed solution may use.	195	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	"Correlation data structure" refers to a data structure configured to store one or more correlation factors and an index for identifying the correlation factor for a particular correlation between two items or things. In one embodiment, a correlation data structure may be a table, an array, a list, a linked list, portion of a memory, a database, or the like. An index for the correlation data structure for correlation factors between memory states may comprise a row identifier for a memory state of correlation data structure table and a correlated memory state may comprise a column of the correlation data structure table.	196	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	In each table, the rows represent a starting memory state and the columns represent an ending memory state for which a correlation exists, that is captured by the correlation factor stored in the cell where the row and column intersect. In one example embodiment, a zero correlation factor may indicate that no correlation, a magnitude of the correlation factor may indicate the strength of the correlation or how much to adjust an attribute (e.g., shift, width, etc.) to account for the correlation, and a positive correlation factor value may represent a positive correlation and a negative correlation factor value may represent a negative correlation.	197	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	Generally, the starting memory state, the row memory state, is a memory state for which an optimal read level has been determined through one or more or parts of a variety of methods. Once that optimal read level is determined for the starting memory state, the shift correlation table 900 and/or width correlation table 1000 may be used to account for the correlation between the starting memory state and the ending memory state and leverage the correlation to determine an optimal read level for the ending memory state.	198	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	By way of example, suppose a starting memory state 902, memory state D, has been determined and a read scan operation is configured to leverage correlations between memory states in determining a read level for an ending memory state 904, memory state G. The read scan operation may consult shift correlation table 900 and locate the row for memory state D and read the value that intersects with the column corresponding to memory state G. The entry is a shift correlation factor 906 and indicates that when starting memory state 902 shifts then, based on a correlation, the ending memory state 904 shifts in an opposite direction, a negative correlation. The negative correlation is indicated by the negative value 150. In this example, the shift correlation factor 906 (e.g., -150 mV as illustrated) may indicate that memory state G experiences a negative shift of 150 mV (shifts down on average voltage by about -150 mV) with respect to memory state D. The read scan operation may leverage this correlation factor to optimize a scanning operation to determine an optimal read level for memory state G.	199	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	FIG. 10 illustrates a width correlation table 1000 having correlation factor that account for width correlations between memory states. As an example, suppose an optimal read level for starting memory state 1002, memory state D, has been determined and a read scan operation is configured to leverage correlations between memory states in determining a read level for an ending memory state 1004, memory state J.	200	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	The read scan operation may consult width correlation table 1000 and locate the row for memory state D and read the value that intersects with the column corresponding to memory state J. The entry is a width correlation factor 1006 and indicates that when starting memory state 1002 widens then, based on a correlation, the ending memory state 1004 also widens by a correlation factor of 1.1016, a positive correlation. The positive correlation is indicated by the positive value greater than 1. In this example, the width correlation factor 1006 (e.g., 1.1016 as illustrated) may indicate that memory state J experiences a widening of 1.1016 times a widening experienced by memory state D. The read scan operation may leverage this correlation factor to optimize a scanning operation to determine an optimal read level for memory state J.	201	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	If a read scan operation determines how a starting memory state (e.g., state D) has shifted or how much the known state widened/narrowed, estimates may be made for other correlated unknown memory states. These estimates may facilitate further read scan operations, or even in certain embodiments, obviate a need for further read scan operations for the ending memory state.	202	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	In this manner, a read scan operation may leverage a correlation between two memory states as a starting point for analysis. This may allow the best location for these read levels to be determined using fewer iterations, or more narrowly spaced read level windows for a valley search operation, in one embodiment. In another embodiment, the location given through use of these tables (shift correlation table 900, width correlation table 1000) may enable optimization of a BES read scan operation.	203	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	FIG. 11 illustrates a read scan operation 1100 in accordance with one embodiment. The read scan operation 1100 illustrated may comprise using an optimal read level determined within first read level window 1102 to more efficiently scan another read level window, such as second read level window 1104.	204	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	A read scan operation may scan read levels within first read level window 1102 checking for a first candidate read level, among candidate read levels 1106, that activates the fewest number of memory cells in relation to other candidate read levels 1106 within the first read level window 1102. This first read level window 1102 may be configured to test candidate read levels 1106 between adjacent memory states 1108, memory state C and memory state D to locate an optimal read level D 1110.	205	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	Once a read scan operation determines read level D 1110, the read scan operation may configure a second read level window 1104 based on a correlation between at least one of the two adjacent memory states 1108 (e.g., C or D) and one or more other adjacent memory states 1108 associated with the second read level window 1104 (e.g., J and K). Advantageously, in one embodiment, the correlation enables the second read level window 1104 to be smaller, e.g., include fewer candidate read levels 1112 than had a correlation not been used to configure the second read level window 1104.	206	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	Next, the read scan operation scans a second read level window 1104. Scanning the configured second read level window 1104 for a second candidate read level may include determining a second candidate read level that activates the fewest number of memory cells in relation to the other candidate read levels 1112 within the second read level window 1104. Once the read scan operation determines an optimal read level D 1110 and optimal read level K 1114, the read scan operation configures a read operation to use optimal read level D 1110 and optimal read level K 1114.	207	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	In one embodiment, configuring the second read level window 1104 may involve determining a correlation factor based on an identifier for one of the two adjacent memory states 1108 associated with the first read level window 1102 (memory state C and memory state D). This identifier may be related a label given the memory state, such as "C" or "D" in the illustrated example, or some other unique identifier for the memory state. Correlation factors, in one embodiment, may be determined using a correlation data structure, such as a shift correlation table 900 and/or width correlation table 1000.	208	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	The read scan operation may apply a determined correlation factor to the second read level window 1104 such that the correlation affects the candidate read levels 1112 of the second read level window 1104. For second read level window 1104, for example, the candidate read levels 1112 #23', #24', #25', #26', and #27', may be centered around a projected threshold voltage, e.g., #25' determined by using the a correlation factor between memory state C and memory state J or memory state C and memory state K, or memory state D and memory state J and memory state D and memory state K.	209	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	In one embodiment, the correlation factor is used to narrow the spacing between candidate read levels 1112, (e.g., #23' through #27') and/or may be used to scan fewer candidate read levels (e.g., 4 versus 7, 4 because #25' is a starting read level). Consequently, second read level window 1104 is smaller, has fewer candidate read levels 1112, than a read level window without using a correlation and/or correlation factor and results in a faster scanning time.	210	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	In one embodiment, applying the correlation factor may comprise multiplying a candidate read level of the second read level window 1104 by the correlation factor. In another embodiment, applying the correlation factor may comprise changing a predefined order for testing/checking the candidate read levels 1112 of the second read level window 1104 such that candidate read levels that incorporate the correlation are used in the scanning.	211	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	In one embodiment, a read scan operation may scan candidate read levels 1112 in a predefined order. For example, the predefined order may alternate between a high threshold voltage candidate read level and low threshold voltage candidate read level (e.g., #24', #26', #23', #27'). In one embodiment, applying a correlation factor to configure second read level window 1104 may include changing the predefined order to a new order based on the correlation factor. For example, suppose a correlation is a negative shift correlation (e.g., negative shift correlation 726). In one embodiment, the read scan operation may be configured to change the predefined order to leverage the negative shift correlation and so the changed order of candidate read levels may be #24', #23', #26', #27'', such that the lower threshold voltage candidates are examined before the higher threshold voltage candidates. In another example, if a correlation indicates a strong likelihood that a memory state may experience widening, the outermost candidates may be used first, and the scan may work its way inward.	212	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	As NAND memory cell storage technologies progress from a single bit per memory cell (single level cell SLC) to multi-level, tri-level, and quad-level operation (storing two, three, and four bits of data, respectively per memory cell), the number of memory states defined within a voltage range (also referred to as a Vt window) increases exponentially. As a non-volatile memory device of memory cells is used, memory states may shift over time to higher threshold voltages or lower threshold voltages. Furthermore, the memory states may spread out widening and overlapping with adjacent memory states. A read scan operation, also referred to as a read level calibration, may be performed both when the non-volatile memory device is manufactured and multiple times thereafter in order to determine suitable voltage thresholds to distinguish memory states from each other and provide accurate read operations.	2	Added by DJM 12 2021	12/22/21, 12:00 AM
View Edit Delete	US10998041B1	However, with the number of memory cells in a memory die increasing as well as the amount of data stored per cell (TLC, MLC, QLC, PLC), read scan operations may become a time consuming process. Read level calibration may be performed in response to environmental changes (such as temperature fluctuations or high device usage) and may distinguish between narrower and narrower margins between memory states. There is, therefore, a need for faster and more efficient read scan operations.	3	Added by DJM 12 2021	12/22/21, 12:00 AM

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