CN115565587B - Method and device for quickly searching threshold voltage, storage medium and SSD (solid State disk) device - Google Patents
Method and device for quickly searching threshold voltage, storage medium and SSD (solid State disk) device Download PDFInfo
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Abstract
The invention relates to the technical field of data storage, and provides a method, a device, a storage medium and SSD equipment for quickly searching threshold voltage, wherein the method comprises the following steps: predicting an initial optimal threshold voltage at an initial search time according to the characteristic of Gaussian distribution of the threshold voltage of the memory cell; acquiring an initial offset value of the initial optimal threshold voltage relative to a default level; and searching an optimal offset value at the current moment in a preset searching range taking the initial offset value as a center at the next searching moment to obtain an optimal threshold voltage at the current moment. According to the invention, the initial optimal threshold voltage is predicted according to the characteristics of the threshold voltage distribution, the initial offset value is calculated, and the range of the scanning optimal threshold voltage is automatically adjusted according to the offset value at the previous moment, so that the read interference effect can be reduced, the rapid search of the threshold voltage is realized, and the threshold voltage searching efficiency is improved.
Description
Technical Field
The present invention relates to the field of data storage technologies, and in particular, to a method, an apparatus, a storage medium, and an SSD device for quickly searching for a threshold voltage.
Background
NAND is used as a mainstream storage medium at present, and has the advantages of high read-write speed, high storage capacity, small power consumption volume, light weight and the like. The memory cells in NAND are characterized by the amount of stored charge, and the reading of NAND data is determined by the read voltage. Taking a Single-Level Cell as an example, when the storage state of a memory Cell is lower than a read voltage, after the read voltage is applied to the gate of the memory Cell, if the memory Cell is in a conductive state, the data recorded by the memory Cell is "1"; conversely, when the storage state of the memory cell is higher than the read voltage, the data recorded by the memory cell is "0" when the memory cell is in the off state after the read voltage is applied to the gate of the memory cell. The read voltage used to distinguish between these two memory states is called the threshold Voltage (VT), and a best threshold voltage can distinguish to a maximum extent whether the data stored in the memory cell is a "0" or a "1", and the best threshold voltage will generally vary with different usage scenarios of NAND, as shown in fig. 1, where the shift of VT with temperature is shown in fig. 1.
In an actual usage scenario, the current best threshold voltage is typically measured by searching for VT. Specifically, in NAND, there is a default read voltage to read data. The default voltage is not always equal to the best threshold voltage, the Read voltage can be changed within a certain range relative to the default voltage by adjusting the register, the data is Read after the Read voltage is changed, and the best Read point is obtained by comparing the actually written data, if the Read voltage of a certain Read Level can obtain the least Bit flip number increment relative to the previous Read voltage, the voltage is considered to be the best threshold voltage, and the method for obtaining the best Read point in this way is called as searching VT.
In the prior art, in order to cope with the VT shift problem, NAND manufacturers provide a method for modifying the read voltage, which is generally to provide an 8-bit register to control the read voltage, the 8-bit register can provide 256 read voltages, and the existing method for searching VT is to change the read voltage and then read out the previously written data in the NAND by setting the value of the register, and then determine the best read voltage by comparing with the actually written data to obtain how many read errors (or bit flip numbers) are. Thus, if it is required to determine the optimal read level by traversing all read voltages, then acquiring the best VT for one page requires setting the registers 256 times and reading 256 pages of data. If the scanning range or accuracy requirement is low, a suitable starting point a, a suitable ending point b, and a suitable scanning accuracy n may be selected, and the number of readings is count= (b-a)/n+1, as shown in fig. 2. It can be seen that the existing VT searching method has excessive Page reading times and has a reading interference effect, so that a result is inaccurate; there is also a problem of too many read pages and low efficiency.
Disclosure of Invention
The present invention has been made in view of the above problems, and is directed to a method, apparatus, storage medium, and SSD device for fast searching for threshold voltages that overcomes or at least partially solves the above problems.
In one aspect of the present invention, there is provided a method of rapidly searching for a threshold voltage, the method comprising:
predicting an initial optimal threshold voltage at an initial search time according to the characteristic of Gaussian distribution of the threshold voltage of the memory cell;
acquiring an initial offset value of the initial optimal threshold voltage relative to a default level;
and searching an optimal offset value at the current moment in a preset searching range taking the initial offset value as a center at the next searching moment to obtain an optimal threshold voltage at the current moment.
Further, predicting the initial optimal threshold voltage at the initial search time according to the characteristic of the threshold voltage of the memory cell in gaussian distribution comprises:
pre-constructing a Gaussian distribution model of threshold voltage;
reading preset data in the memory unit by using two preset threshold voltages, and obtaining bit turning number of the read data corresponding to the two preset threshold voltages;
calculating parameters of the Gaussian distribution model according to two preset threshold voltages and the bit turning number of corresponding read data to obtain a Gaussian distribution function of the threshold voltage of the memory cell;
and predicting the initial optimal threshold voltage by adopting the Gaussian distribution function.
Further, the gaussian distribution model is as follows:
Further, the method further comprises:
searching the optimal offset value at the current moment in a preset searching range taking the optimal offset value corresponding to the previous searching moment as the center at any subsequent searching moment to obtain the optimal threshold voltage at the current moment.
Further, the method further comprises:
determining a scanning interval n according to a sampling time interval searched by multiplying a preset maximum Vt shift rate by a threshold voltage;
the preset searching range taking the optimal offset value as the center is a range taking the optimal offset value as the midpoint and taking + -n in front and back.
In another aspect of the present invention, there is provided an apparatus for rapidly searching for a threshold voltage, the apparatus comprising:
the prediction module is used for predicting an initial optimal threshold voltage at the initial searching moment according to the characteristic of the Gaussian distribution of the threshold voltage of the storage unit;
the acquisition module is used for acquiring an initial offset value of the initial optimal threshold voltage relative to a default level;
and the searching module is used for searching the optimal offset value at the current moment in a preset searching range taking the initial offset value as the center at the next searching moment so as to obtain the optimal threshold voltage at the current moment.
Further, the prediction module includes:
the model building unit is used for pre-building a Gaussian distribution model of the threshold voltage;
the acquisition unit is used for reading preset data in the storage unit with two preset threshold voltages and acquiring bit flip numbers of the read data corresponding to the two preset threshold voltages;
the calculation unit is used for calculating parameters of the Gaussian distribution model according to two preset threshold voltages and the bit turning number of corresponding read data to obtain a Gaussian distribution function of the threshold voltage of the storage unit;
and the prediction unit is used for predicting the initial optimal threshold voltage by adopting the Gaussian distribution function.
Further, the apparatus further comprises:
the configuration module is used for determining a scanning interval n according to a sampling time interval searched by multiplying a preset maximum Vt shift rate by a threshold voltage;
the preset searching range taking the optimal offset value as the center is a range taking the optimal offset value as the midpoint in front and back to achieve +/-n.
In a third aspect of the invention, a computer readable storage medium is provided, on which a computer program is stored which, when being executed by a processor, implements the steps of the method of rapidly searching for threshold voltages as above.
In a fourth aspect of the present invention there is also provided an SSD device comprising a storage controller including a memory, a processor and a computer program stored on the memory and executable on the processor, the processor executing the steps of the method of implementing the fast search for threshold voltages as above.
According to the method, the device, the storage medium and the SSD device for quickly searching the threshold voltage, the initial optimal threshold voltage is predicted according to the characteristics of threshold voltage distribution, the initial offset value is calculated, the range for scanning the optimal threshold voltage is automatically adjusted according to the offset value at the previous moment, the read interference effect can be reduced, the quick search of the threshold voltage is realized by reducing the scanning range of the optimal threshold voltage, and the threshold voltage searching efficiency is improved.
The foregoing description is only an overview of the present invention, and is intended to be implemented in accordance with the teachings of the present invention in order that the same may be more clearly understood and to make the same and other objects, features and advantages of the present invention more readily apparent.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to designate like parts throughout the figures. In the drawings:
FIG. 1 is a schematic diagram of a shift in threshold voltage with temperature;
FIG. 2 is a diagram of a search threshold voltage in the prior art;
FIG. 3 is a flowchart of a method for fast searching for threshold voltages according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a fast search threshold voltage according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of predicting an optimal threshold voltage based on a Gaussian distribution of threshold voltages according to an embodiment of the present invention;
fig. 6 is a block diagram of a device for fast searching threshold voltage according to an embodiment of the present invention.
Detailed Description
Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
As used herein, the singular forms "a", "an", "the" and "the" are intended to include the plural forms as well, unless expressly stated otherwise, as understood by those skilled in the art. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It will be understood by those skilled in the art that all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs unless defined otherwise. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
Fig. 3 schematically illustrates a flow chart of a method of fast searching for threshold voltages in accordance with one embodiment of the present invention. Referring to fig. 3, the method for quickly searching for a threshold voltage according to an embodiment of the present invention specifically includes the following steps:
s11, predicting an initial optimal threshold voltage at an initial searching time according to the characteristic of the threshold voltage of the memory cell in Gaussian distribution.
In NAND flash memory, the present invention predicts the initial optimal threshold voltage at the initial search time based on the Gaussian distribution of the threshold voltage of the memory cell. The NAND flash memory is a serial memory cell flash memory structure in which data information is recorded by changing the charge amount of a memory layer in a memory cell. The threshold voltage VT is threshold voltage, and the NAND flash memory can make the memory cells at different threshold voltages according to the data content when writing, so that different read voltages are applied when reading, and then the data stored in the memory cells can be judged through the on or off state of the memory device.
S12, acquiring an initial offset value of the initial optimal threshold voltage relative to a default level. The default level is the default read voltage, which is the read voltage that is used for the first time each time the flash memory is read.
And S13, searching an optimal offset value at the current moment in a preset searching range with the initial offset value as a center at the next searching moment to obtain an optimal threshold voltage at the current moment.
Further, in the threshold voltage searching process, at any subsequent searching time, searching the optimal offset value at the current time within a preset searching range taking the optimal offset value corresponding to the previous searching time as the center, so as to obtain the optimal threshold voltage at the current time.
In the embodiment of the present invention, in the process of tracking the best threshold voltage of one Read Level, the change of the threshold voltage along with time is shown in fig. 4, T0 to T4 are the current conditions of different moments VT, R0 is the default voltage of Read Level 0, value0 represents the offset size of VT, that is, the offset size is offset by a large range of value0 with respect to R0, and the identified range in fig. 4 is the offset size. The method for quickly searching the threshold voltage can quickly acquire the best threshold voltage at the moment.
According to the method for quickly searching the threshold voltage, the initial optimal threshold voltage is predicted according to the characteristics of threshold voltage distribution, the initial offset value is calculated, the range of the optimal threshold voltage is automatically adjusted and scanned according to the offset value at the previous moment, the searching range of the optimal threshold voltage at the next moment can be determined according to the optimal threshold voltage at the previous moment, the searching range of the optimal threshold voltage can be searched, the searching range of the optimal threshold voltage can be shortened, the reading Page times are reduced, the reading interference effect is further reduced, quick searching of the threshold voltage is achieved, and the searching efficiency of the threshold voltage is improved.
In the embodiment of the present invention, step S11 predicts an initial optimal threshold voltage at an initial search time according to a gaussian distribution characteristic of threshold voltages of memory cells, and specifically includes steps not shown in the following drawings:
s111, a Gaussian distribution model of threshold voltage is built in advance, and the Gaussian distribution model is as follows:
wherein μ and σ are parameters of the Gaussian distribution model, x is threshold voltage, and f (x) is the corresponding bit flip number when the data is read by using the threshold voltage x.
S112, reading preset data in the memory cell with two preset threshold voltages, and obtaining bit flip numbers of the read data corresponding to the two preset threshold voltages;
s113, calculating parameters of the Gaussian distribution model according to two preset threshold voltages and the bit turning number of corresponding read data to obtain a Gaussian distribution function of the threshold voltage of the memory cell;
s114, predicting the initial optimal threshold voltage by adopting the Gaussian distribution function.
In the embodiment of the invention, the distribution of Vt of each storage unit in one page is Gaussian, the preset data in the storage unit is read by the preset two threshold voltages, the bit turning number corresponding to the two threshold voltages is read, then the parameters of the Gaussian distribution are obtained, the approximate position of the optimal decision level can be judged, and the accurate optimal decision level can be obtained in a follow-up tracking mode. Specifically, the bit flip number b0 at the a0 position and the bit flip number b1 at the a1 position are measured, and as shown in fig. 5, the gaussian distribution model is carried in to calculate μ and σ, and the optimal decision level is predicted according to the gaussian distribution function of this level.
The invention calculates the next scanning range by collecting the best reading point. Specifically, at time T0, the characteristic of the gaussian distribution of the threshold voltage finds the current best threshold voltage, and records the offset value0 of the current best threshold voltage relative to the default level.
At time T1, according to the offset value0, finding out the best threshold voltage value1 in the preset searching range by taking value0 as a midpoint. In the embodiment of the invention, a scanning interval n is determined according to a sampling time interval searched by multiplying a preset maximum Vt shift rate by a threshold voltage; the preset searching range taking the optimal offset value as the center is a range taking the optimal offset value as the midpoint in front and back to achieve +/-n. Specifically, the scanning interval n is obtained by multiplying the estimated maximum Vt shift rate by the sampling time interval, the range of ±n is taken forward and backward with value0 as the midpoint, and the best threshold voltage value1 is found out in the range of 2 n. The invention can freely control the sampling frequency without waiting for RBER to change to the next interval.
Similarly, at time T2, according to value1, taking value1 as the midpoint and taking the range of ±n from front to back, finding the best threshold voltage within the range of 2 n.
And searching the best threshold voltage in sequence until the test is finished.
In the embodiment of the present invention, the implementation of the threshold voltage Vt tracking is explained by taking the unit memory cell SLC as an example, and it is understood that the method is equally applicable to MLC, TLC, QLC and other NAND types. The unit memory Cell is named SLC (Single-Level Cell), and a Single physical memory device in the NAND flash memory can store one bit of binary data 1 or 0. Two-bit memory Cell the english name is MLC (Multi-Level Cell), and a single physical memory device in NAND flash memory can store two bits of binary data 11, 01, 10, 00. Three-bit memory Cell the english name is TLC (ternary-Level Cell), and a single physical memory device in NAND flash memory can store three-bit binary data 111, 110, 101, 100, 011, 010, 001, 000. Four-bit memory cell: the english name is QLC (Quad-Level Cell), and a single physical memory device in NAND flash memory can store four-bit binary data 1111, 1110, 1101, 1100, 1011, 1010, 1001, 1000, 0111, 0110, 0101, 0100, 0011, 0010, 0001, 0000.
According to the method, the device, the storage medium and the SSD device for quickly searching the threshold voltage, the initial optimal threshold voltage is predicted according to the characteristics of threshold voltage distribution, the initial offset value is calculated, the range of the scanned optimal threshold voltage is automatically adjusted according to the offset value at the previous moment, the read interference effect can be reduced, the quick search of the threshold voltage is realized, and the threshold voltage searching efficiency is improved.
For the purposes of simplicity of explanation, the methodologies are shown and described as a series of acts, it is to be understood and appreciated by one of ordinary skill in the art that the methodologies are not limited by the order of acts, as some acts may, in accordance with the methodologies, take place in other order or concurrently. Further, those skilled in the art will appreciate that the embodiments described in the specification are presently preferred embodiments, and that the acts are not necessarily required by the embodiments of the invention.
Fig. 6 schematically illustrates a structural diagram of an apparatus for fast searching for threshold voltages according to an embodiment of the present invention. Referring to fig. 6, the apparatus for fast searching for a threshold voltage according to the embodiment of the present invention specifically includes a prediction module 201, an acquisition module 202, and a search module 203, where:
a prediction module 201, configured to predict an initial optimal threshold voltage at an initial search time according to a characteristic of a gaussian distribution of threshold voltages of the memory cells;
an obtaining module 202, configured to obtain an initial offset value of the initial optimal threshold voltage relative to a default level;
the searching module 203 is configured to search, at a next searching time, for an optimal offset value at a current time within a preset searching range centered on the initial offset value, so as to obtain an optimal threshold voltage at the current time.
In the embodiment of the present invention, the prediction module specifically includes a model building unit 201, an obtaining unit 202, a calculating unit 203, and a prediction unit 204, where:
a model construction unit 201 for constructing a gaussian distribution model of threshold voltages in advance;
an obtaining unit 202, configured to read preset data in the storage unit with two preset threshold voltages, and obtain bit flip numbers of the read data corresponding to the two preset threshold voltages;
the calculating unit 203 is configured to calculate parameters of the gaussian distribution model according to two preset threshold voltages and the bit flip number of the corresponding read data, so as to obtain a gaussian distribution function of the threshold voltages of the memory cells;
a prediction unit 204, configured to predict the initial optimal threshold voltage using the gaussian distribution function.
In the embodiment of the invention, the device further comprises a configuration module, wherein the configuration module is used for determining a scanning interval n according to a sampling time interval searched by multiplying a preset maximum Vt offset rate by a threshold voltage; the preset searching range taking the optimal offset value as the center is a range taking the optimal offset value as the midpoint in front and back to achieve +/-n.
For the device embodiments, since they are substantially similar to the method embodiments, the description is relatively simple, and reference is made to the description of the method embodiments for relevant points.
Furthermore, embodiments of the present invention provide a computer-readable storage medium, on which a computer program is stored, which program, when being executed by a processor, implements the steps of the method as described above.
In this embodiment, the device for rapidly searching for threshold voltages may be stored in a computer readable storage medium if implemented in the form of a software functional unit and sold or used as a separate product. Based on such understanding, the present invention may implement all or part of the flow of the method of the above embodiment, or may be implemented by a computer program to instruct related hardware, where the computer program may be stored in a computer readable storage medium, and when the computer program is executed by a processor, the computer program may implement the steps of each of the method embodiments described above. Wherein the computer program comprises computer program code which may be in source code form, object code form, executable file or some intermediate form etc. The computer readable medium may include: any entity or device capable of carrying the computer program code, a recording medium, a U disk, a removable hard disk, a magnetic disk, an optical disk, a computer Memory, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), an electrical carrier signal, a telecommunications signal, a software distribution medium, and so forth. It should be noted that the computer readable medium contains content that can be appropriately scaled according to the requirements of jurisdictions in which such content is subject to legislation and patent practice, such as in certain jurisdictions in which such content is subject to legislation and patent practice, the computer readable medium does not include electrical carrier signals and telecommunication signals.
In addition, an embodiment of the present invention further provides an SSD device, where the device includes a storage controller, where the storage controller includes a memory, a processor, and a computer program stored on the memory and executable on the processor, where the processor implements the steps of the method as described above when the processor executes the program. Such as steps S11-S13 shown in fig. 3.
According to the method, the device, the storage medium and the SSD device for quickly searching the threshold voltage, the initial optimal threshold voltage is predicted according to the characteristics of threshold voltage distribution, the initial offset value is calculated, the range of the scanned optimal threshold voltage is automatically adjusted according to the offset value at the previous moment, the read interference effect can be reduced, the quick search of the threshold voltage is realized, and the threshold voltage searching efficiency is improved.
The apparatus embodiments described above are merely illustrative, wherein the elements illustrated as separate elements may or may not be physically separate, and the elements shown as elements may or may not be physical elements, may be located in one place, or may be distributed over a plurality of network elements. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art will understand and implement the present invention without undue burden.
From the above description of the embodiments, it will be apparent to those skilled in the art that the embodiments may be implemented by means of software plus necessary general hardware platforms, or of course may be implemented by means of hardware. Based on this understanding, the foregoing technical solution may be embodied essentially or in a part contributing to the prior art in the form of a software product, which may be stored in a computer readable storage medium, such as ROM/RAM, a magnetic disk, an optical disk, etc., including several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the method described in the respective embodiments or some parts of the embodiments.
Furthermore, those skilled in the art will appreciate that while some embodiments herein include some features but not others included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention and form different embodiments. For example, any of the claimed embodiments can be used in any combination.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (9)
1. A method of rapidly searching for a threshold voltage, the method comprising:
in the process of tracking the optimal threshold voltage of one Read Level, predicting the initial optimal threshold voltage at the initial searching moment according to the Gaussian distribution characteristic of the threshold voltage of the memory cell;
acquiring an initial offset value of the initial optimal threshold voltage relative to a default level;
searching an optimal offset value at the current moment in a preset searching range taking the initial offset value as a center at the next searching moment to obtain an optimal threshold voltage at the current moment;
determining a scanning interval n according to a sampling time interval searched by multiplying a preset maximum Vt shift rate by a threshold voltage;
the preset searching range taking the initial offset value as the center is a range taking the initial offset value as the midpoint and taking + -n in front and back.
2. The method of claim 1, wherein predicting an initial optimal threshold voltage at an initial search time based on a gaussian distribution of threshold voltages of memory cells comprises:
pre-constructing a Gaussian distribution model of threshold voltage;
reading preset data in the memory unit by using two preset threshold voltages, and obtaining bit turning number of the read data corresponding to the two preset threshold voltages;
calculating parameters of the Gaussian distribution model according to two preset threshold voltages and the bit turning number of corresponding read data to obtain a Gaussian distribution function of the threshold voltage of the memory cell;
and predicting the initial optimal threshold voltage by adopting the Gaussian distribution function.
3. The method according to claim 1 or 2, characterized in that the gaussian distribution model is as follows:
4. The method according to claim 1, wherein the method further comprises:
searching the optimal offset value at the current moment in a preset searching range taking the optimal offset value corresponding to the previous searching moment as the center at any searching moment to obtain the optimal threshold voltage at the current moment.
5. The method according to claim 4, wherein the method further comprises:
the preset searching range taking the optimal offset value as the center is a range taking the optimal offset value as the midpoint and taking + -n in front and back.
6. An apparatus for fast searching for a threshold voltage, the apparatus comprising:
the prediction module is used for predicting the initial optimal threshold voltage at the initial searching moment according to the Gaussian distribution characteristic of the threshold voltage of the memory cell in the process of tracking the optimal threshold voltage of one Read Level;
the acquisition module is used for acquiring an initial offset value of the initial optimal threshold voltage relative to a default level;
the searching module is used for searching an optimal offset value at the current moment in a preset searching range taking the initial offset value as a center at the next searching moment so as to obtain an optimal threshold voltage at the current moment;
the configuration module is used for determining a scanning interval n according to a sampling time interval searched by multiplying a preset maximum Vt shift rate by a threshold voltage;
the preset searching range taking the initial offset value as the center is a range taking the initial offset value as the midpoint in front and back to take + -n.
7. The apparatus of claim 6, wherein the prediction module comprises:
the model building unit is used for pre-building a Gaussian distribution model of the threshold voltage;
the acquisition unit is used for reading preset data in the storage unit with two preset threshold voltages and acquiring bit flip numbers of the read data corresponding to the two preset threshold voltages;
the calculation unit is used for calculating parameters of the Gaussian distribution model according to two preset threshold voltages and the bit turning number of corresponding read data to obtain a Gaussian distribution function of the threshold voltage of the storage unit;
and the prediction unit is used for predicting the initial optimal threshold voltage by adopting the Gaussian distribution function.
8. A computer readable storage medium, on which a computer program is stored, characterized in that the computer program, when being executed by a processor, implements the steps of the method according to any of claims 1-5.
9. An SSD device comprising a storage controller, the storage controller comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the steps of the method of any of claims 1-5 when the computer program is executed.
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