Abstract:
A method for recording a duration of use of a data block is disclosed, as well as a data storage device implementing that method. The data block is either an in-use data block or an empty data block. The method includes steps of: receiving and writing data into one of the in-use data blocks and writing a program time and a time interval of the data into the in-use data block. Wherein the time interval is a difference between the program time and an initial program time of the in-use data block, and the initial program time was recorded when the in-use data block wrote a first piece of data.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a method for recording a duration of use of a data block, and more particularly to a method for recording a duration of use of a data block in a non-volatile memory, a method for managing data block using the same and related device. 
       BACKGROUND OF THE INVENTION 
       [0002]    Non-volatile memory is an electronic memory device with specific abilities such as maintaining data without extra power, fast data access and shockproof. Therefore, non-volatile memory is widely used in memory cards, solid state drives (SSD) and portable multimedia devices. Non-volatile memory includes a plurality of data blocks for storing data. Specifically, according to the using situation, each data block may be defined as an in-use data block or an empty data block; wherein in-use data block is referred to as a data block saving valid data and empty data block is referred to as a data block not saving valid data. Therefore, a data block is changed from an empty data block to an in-use data block once a first record of data is written therein. Generally speaking, an in-use data block can be repeatedly written with data until the storing space thereof is full with data; and consequentially, an incoming data will be saved into the next empty data block. In generally, an in-use data block is in a word line open state, and is changed from in a word line open state to in a word line close state once the in-use block has no any storing space for data. However, when a data block is operated in the word line open state for too long, the non-volatile memory may have data retention or data distortion problems resulted by the effects of electricity of the non-volatile memory itself and impact of continuous access on the non-volatile memory. On the contrary, the data retention problem seldom occurs when a data block is in the word line close state. Therefore, it is quite important to develop method and related device able to solve the data retention problems resulted by operating the data block in the word line open state for too long. 
       SUMMARY OF THE INVENTION 
       [0003]    Accordingly, one objective of the present invention is to provide method for recording a duration of use of a data block and related devices, which are able to avoid data damage resulted by the data block having a too-long open time. 
         [0004]    The present invention provides a method for recording a duration of use of a data block of a non-volatile memory. The non-volatile memory includes a plurality of in-use data blocks and empty data blocks. The data block is either the in-use data blocks or the empty data blocks. The method includes steps of: receiving and writing data into one of the in-use data blocks; and writing a program time of the data and a time interval into the in-use data block, wherein the time interval is a difference between the program time of the data and an initial program time of the in-use data block, and the initial program time is recorded when a first piece of data is written into the in-use data block. 
         [0005]    The present invention further provides a method for managing a data block of a non-volatile memory. The non-volatile memory includes a plurality of in-use data blocks and empty data blocks. The data block is either the in-use data blocks or the empty data blocks. The method includes steps of: generating a duration of use of the in-use data block according to a method for recording the duration of use of the data block of the non-volatile memory; and changing an empty data block into a second in-use data block and writing data saved in the in-use data block into the second in-use data block when the duration of use is greater than a threshold. The duration of use is a difference between a current time and an initial program time of the in-use data block. 
         [0006]    The present invention still further provides a data storage device, which includes a non-volatile memory and a memory controller. The non-volatile memory includes a plurality of data blocks. The data blocks are either in-use data blocks or empty data blocks. The memory controller is electrically coupled to the non-volatile memory and configured to write data, program times and time intervals of the data into one of the in-use data blocks. The time interval is a difference between the program time and an initial program time of one of the in-use data blocks. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Other advantages, objectives and features of the present invention will become apparent from the following description referring to the attached drawings. 
           [0008]      FIG. 1A  is a schematic block view of a data storage device in accordance with an embodiment of the present invention; 
           [0009]      FIG. 1B  is a schematic view of a non-volatile memory in accordance with an embodiment of the present invention; 
           [0010]      FIG. 2A  is a flowchart of a method for recording a duration of use of a data block in accordance with the first embodiment of the present invention; 
           [0011]      FIG. 2B  is a flowchart of a method for recording a duration of use of a data block in accordance with the second embodiment of the present invention; and 
           [0012]      FIG. 3  is a flowchart of a method for managing data blocks by using the above-described method for recording a duration of use of a data block in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0013]    The present invention will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for purpose of illustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed. 
         [0014]    Please refer to  FIG. 1A , which is a schematic block view of a data storage device in accordance with an embodiment of the present invention. As shown, the data storage device  10  of the present embodiment is able to communicate with an external host  20  and configured to program received written data according to a write instruction issued from the host  20 . The host  20  may be an electronic device such as a desktop or a tablet computer. The data storage device  10  includes a memory controller  11  and a non-volatile memory  12 . The non-volatile memory  12  may be a flash memory, MRAM (Magnetic RAM), FRAM (Ferroelectric RAM), PCM (Phase Change Memory), STTRAM (Spin-Transfer Torque RAM), ReRAM (Resistive RAM) and Memristor. The memory controller  11  is electrically coupled to the host  20  and the non-volatile memory  12 . The memory controller  11  includes a first communication interface  111 , a second communication interface  112  and a microprocessor  113 . The microprocessor  113  is electrically coupled to the first communication interface  111  and the second communication interface  112 . The memory controller  11  is in communication with the host  20  through the first communication interface  111  so as to receive the aforementioned write instruction and data to be programmed. The memory controller  11  is further in communication with the non-volatile memory  12  through the second communication interface  112  so as to access the non-volatile memory  12 . In one embodiment, the first communication interface  111  may be serial advanced technology attachment (SATA), universal serial bus (USB), peripheral component interconnect express (PCI Express), non-volatile memory express (NVMe), universal flash storage (UFS), embeddedMultiMedia card (eMMC) or secure digital input/output (SDIO). In one embodiment, the second communication interface  112  may be open NAND flash interface (ONFI) or Toggle. 
         [0015]    Next, please refer to  FIG. 1B , which is a schematic view of the non-volatile memory  12  (or the flash memory  12 ) in accordance with an embodiment of the present invention. As shown, the non-volatile memory  12  includes a plurality of data blocks  121  (herein only one data block  121  is exemplarily shown). Each data block  121  includes a plurality of data pages  122   a,    122   b,    122   c,  . . . , and  122   n;  wherein a, b, c, . . . , and n are integers, such as a=1, b=2, c=3 and n=256 in one embodiment. Word lines (not sown) are used to control the access of the data page  122   a - 122   n.  Specifically, for the flash memory with single-level cell (SLC), each word line can control the access of one data page; for the flash memory with multi-level cell (MLC), each word line can control the access of two data page; for the flash memory with triple-level cell (TLC), each word line can control the access of three data page; and so on. Hereafter the flash memory with single-level cell will be taken as an example for the description of the present invention; however, it is understood that the present invention is not limited thereto. 
         [0016]    With the development of technology, today each one of the data pages  122   a - 122   n  can store more than one record of data. For example, each one of the data pages  122   a - 122   n  may store eight records of 512-byte data. However, to simplify the description of the present invention, it is assumed that each one of the data pages  122   a - 122   n  in the present embodiment can store only one record of data; but the present invention is not limited thereto. In addition, besides data areas  123   a ,  123   b,    123   c,  . . . , and  123   n  for storing data, the data pages  122   a - 122   n  further include spare areas  124   a,    124   b,    124   c,  . . . , and  124   n  for storing extra data, such as metadata, respectively. In the present embodiment, specifically, the spare areas  124   a - 124   n  are used to store program time and time intervals of the data pages  122   a - 122   n,  respectively. In the present invention, the time interval is referred to as a time difference between the programming time of the first record of data and the program time of the current record of data (written into the same data block). As illustrated in  FIG. 1B , for example, the programming time PTa in the data page  122   a  is 00:00 which indicates that the first record of data is programmed into the data page  122   a  at time 00:00; the program time PTb in the data page  122   b  is 03:00 which indicates that the second record of data is programmed into the data page  122   b  at time 03:00, therefore the time interval Tlb of the second record of data is 3 (unit in hours); and the program time PTc in the data page  122   c  is 05:00 which indicates that the third record of data is written into the data page  122   c  at time 05:00, therefore the time interval Tlc of the third record of data is 5. In the present invention, it is understood that more bits are used for recording the time interval, the more accurate the time interval is. For example, if a sufficient number of bits are used, the time interval may have a unit in minutes in another embodiment. 
         [0017]    In addition, due to the continuity of data, the data received by the data block  121  is programmed into the data pages  122   a - 122   n  in sequence. Therefore, if there are three continuous records of data sequentially programmed into the same data block, the first record of data may be defined as the prior data; the second record of data may be defined as the current data; and the third record of data may be defined as the later data. Accordingly, the prior data, the current data and the later data are sequentially programmed into the prior data page (e.g., the data page  122   a ), the current data page (e.g., the data page  122   b ) and the later data page (e.g., the data page  122   c ), respectively. Further, the data page  122   a  saves the prior program time and the prior time interval of the prior data; the data page  122   b  saves the current program time and the current time interval of the current data; and the data page  122   c  saves the later program time and the later time interval of the later data. To simplify the description of the present invention, the data, program time and time interval are referred to the current data, current program time and current time interval, respectively, if no specifying. Further, if there are only three data pages (e.g., the data pages  122   a,    122   b  and  122   c ) saved with data in the data blocks  121 , the third data page (e.g., the data page  122   c ) is referred as the latest data page in the data block  122 . Once the fourth data page (e.g., the data page  122   d ) saves data, the fourth data page (e.g., the data page  122   d ) replaces the third data page (e.g., the data page  122   c ) as the latest data page in the data block  122 , and so on. 
         [0018]      FIG. 2A  is a flowchart of a method for recording a duration of use of a data block in accordance with the first embodiment of the present invention. Please refer to  FIGS. 1A, 1B and 2A  together. First, when the data storage device  10  receives the write instruction with the written data from the host  20 , the microprocessor  113  in  FIG. 1A  executes a data programming procedure (step  201 ) to program the written data into the data block  121 . The microprocessor  113  determines whether the data shall be programmed into an empty data block or not (step  203 ). When the determining result obtained in step  203  is Yes which indicates that the written data shall be programmed into an empty data block. The microprocessor  113  programs the written data into the data area  123   a  of the data page  122   a  of the data block  121 , resets the time interval TIa of the data page  122   a  (or the current data) to 0 (step  205 ) and updates the program time PTa by the current time (step  209 ). Then, the microprocessor  113  saves the time interval TIa and the program time PTa into the spare area  124   a  of the data page  122   a  (step  211 ). As illustrated in  FIG. 1B , for example, the spare area  124   a  of the data page  122   a  is written with the time interval TIa (e.g., 0) and the program time PTa (e.g., 00:00). Then, the microprocessor  113  ends the data writing procedure (step  213 ). Because of the data page  122   a  is the first data page written with data in the data block  121  (or, the data page  122   a  is written with the first record of data), the program time PTa of the data page  122   a  is also referred as the initial program time of the data block  121 . Further, because of being written with data, the data block  121  is changed from an empty data block to an in-use data block, and the subsequent data will continue to be written into the data block  121  until all the data pages therein are written with data. 
         [0019]    Alternatively, when the determining result obtained in step  203  is No which indicates that the data block  121  to be written with data is an in-use data block, the microprocessor  113  writes the data into the first empty data page (e.g., the data page  122   b ) in the data block  121 , as illustrated in  FIG. 1B . Therefore, the being-written data is defined as the current data; the data page  122   b  is defined as the current data page; the data saved in the data page  122   a  is defined as the prior data; and the data page  122   a  is defined as the prior data page. Herein it is assumed that the current time is 03:00; therefore, the microprocessor  113  calculates the difference between the current time (e.g., 03:00) and the program time PTa (e.g., 00:00) of the prior data to generate a time gap (e.g., 3−0=3) and adds the time gap (e.g., 3) with the time interval TIa (e.g., 0) of the prior data page  122   a  to obtain the time interval of the current data (or the time interval TIb (e.g., 3+0=3) of the data page  122   b  (step  207 ). Then, step  209  is performed to update the program time PTb by the current time, that is, the program time PTb is updated to 03:00. Then, step  211  is performed to write the program time PTb and the time interval TIb of the data page  122   b  into the spare area  124   b  of the data page  122   b.  Then, step  213  is performed to end the data writing procedure. 
         [0020]    When another record of data is written into the data page  122   c , steps  207 ,  209 ,  211  and  213  are repeated so that the microprocessor  113  can obtain the program time PTc (e.g., 05:00) of the data page  122   c  and the time interval TIc (e.g., 5) and then saves the program time PTc (e.g., 05:00) and the time interval TIc (e.g., 5) into the spare area  124   c  of the data page  122   c.  According to the above description, it is understood that the data storage device  10  of the present embodiment can record the program time of the written data of each data page (or the program time of each record of data) in one data block and the time interval between the program time of each data page and the initial program time (or the time interval of each record of data); wherein the aforementioned time interval is regarded as the duration of use of the data block  121  in the present invention. 
         [0021]    During the data writing procedure, the data storage device  10  may be accidently powered off and then powered on; and consequentially the program time and the time interval may be lost or reset to 0, which may lead to the re-powered-on data storage device  10  not able to calculate the duration of use of the data block  121  correctly. Therefore, please refer to  FIG. 2B , which is a flowchart a method for recording a duration of use of a data block in accordance with the second embodiment of the present invention. As shown in  FIG. 2B , when the data storage device  10  is accidently powered off and then powered on and the determining result obtained in step  203   a  is Yes which indicates that the data block  121  to be written data is an in-use data block, the microprocessor  113  determines the latest data page in the data block  121  and reads the program time and the time interval of the latest data page (step  206 ). Herein it is assumed that the latest data page in the data block  121  is the data page  122   b;  therefore, the microprocessor  113  reads the program time PTb and the time interval TIb of the latest data page  122   b  and obtains the time interval TIc of the data page  122   c  according to the difference between the current time and the program time PTb and the time interval TIb. Then, step  209  is performed to update the program time PTc by the current time. Then, step  211  is performed to write the program time PTc and the time interval TIb into the spare area  124   c  of the data page  122   c.  Then, step  213  is performed to end the data writing procedure. 
         [0022]    In the present invention, the microprocessor  113  can obtain information about the prior data page relatively easily; therefore, when writing the current data, the microprocessor  113  can calculate the time interval of the current data based on the information about the prior data page. In one embodiment, the data page  122   a  only records the respective program time PTa (that is, the initial program time), and the microprocessor  113  obtains the duration of use according to the difference between the current time and the program time PTa of the data page  122   a . Namely, in the present embodiment, the calculations of the program time and the time interval are omitted and consequentially the writing times and spaces for the program time and the time interval are saved. 
         [0023]    Referring to  FIG. 3 , which is a flowchart of a method for managing data blocks by using the above-described method for recording a duration of use of a data block in accordance with an embodiment of the present invention. Specifically, the method for managing data blocks of the present embodiment calculates the duration of use of the data block  121  according to the program time, the time interval and the current time and then determines whether there is a need to move or write the data in the in-use data block  121  to an empty data block according to the obtained duration of use. As shown in  FIG. 3 , first, the microprocessor  113  executes a data block managing procedure (step  301 ). In one embodiment, the data block managing procedure may be executed in some specific situations such as the data storage device  10  is idle or in a power saving mode or the data reading procedure is executed. Then, the microprocessor  113  reads the data saved in the data pages  122   a - 122   n  to determine the latest data page in the data block  121  and obtains the program time and the time interval of the latest data page (step  303 ). As illustrated in  FIG. 1B , for example, the data page  122   c  is the latest data page. Then, the microprocessor  113  calculates the difference between the current time (e.g., 23:00) and the program time PTc (e.g., 05:00) to obtain the time gap (e.g., 23−5=18) and adds the time gap (e.g., 18) with the time interval TIc (e.g., 5) of the data page  122   c  to obtain the duration of use (e.g., 18+5=23) (step  305 ). Namely, there are 23 hours between the current time and the initial program time of the data block  121 ; that is, the data block  121  is under the word line open state for 23 hours. Then, the microprocessor  113  determines whether the duration of use is greater than a predetermined threshold (step  307 ). Preferably, the predetermined threshold is set to the time length under which the data block in the word line open state can operate normally, for example, 240 hours. In one embodiment, the predetermined threshold can be adjusted with the increments of the erase count or the read count. For example, the predetermined threshold is set to 240 when the erase count is smaller than 100 or the read count is smaller than 1000; and the predetermined threshold is set to 140 when the erase count is greater than 100 or the read count is greater than 1000; but the present invention is not limited thereto. When the determining result obtained in step  307  is Yes which indicates that the duration of use is greater than the predetermined threshold, it is determined that the data block  121  is in the word line open state for too long and consequentially data damage may occur; thus, the microprocessor  113  writes all the data in the data block  121  into an empty data block and erases all the data in the data block  121  (step  309 ), thereby avoiding the damage of the data saved in the current data block  121 . Thus, the data block  121  is changed from an in-use data block to an empty data black and waits for being selected to receive another record of data. Alternatively, when the determining result obtained in step  307  is No which indicates that the duration of use is not greater than the predetermined threshold, it is determined that duration of use of the data lock  121  is in a normal or reasonable range, then, the microprocessor  113  ends the data block managing procedure (step  311 ). 
         [0024]    In summary, besides storing the written data, each data page in an in-use data block further saves the respective program time and the interval time (or the difference between the program time and the initial program time). Therefore, the data storage device of the present invention can calculate the duration of use of the data block and accordingly determines whether there is a need to move or write the data in the in-use data block to an empty data block. As a result, the data damage resulted by operating the data block under the word line open state for a long time is avoided. 
         [0025]    While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.