Abstract:
A method of reducing the frequency of erasing steps of a flash memory is described. A linking method under a mother and a child block architecture for building a check area and a logic page of the child block in order to reduce the frequency of erasing steps of the flash memory so that the service life of the flash memory can be extended and also the processing speed can be promoted.

Description:
BACKGROUND OF THE INVENTION 
   1. The Field of the Invention 
   The present invention relates to a linking method under the mother and child block architecture for building check area and logic page of the child block for reducing the frequency of the erasing steps of the flash memory for extending the service life and to promote the operating speed thereof. 
   2. Description of the Related Art 
   The flash memory has been advantageously used in a variety of portable devices because of its unique characteristics, such as, low power consumption, non-volatile, high shock-tolerance and high storage density, gradually replacing EEPROM or other memory devices that requires a battery for operation thereof. Additionally, with the dramatic improvement of the semi-conductor technologies, the flash memory can achieve higher and better storage density and transmission speed, and accordingly the flash memory desirably replaces the traditional storage media, such as the hard disk driver in many applications. 
   However, the flash memory has certain limitation, in that, requires new space management for storage system. Besides, a new erasing method is required for evenly erasing the storage area in order to reduce the frequency of erasing, and thus the service life of the flash memory can be substantially extended and the power consumption of the system can be accordingly reduced. In the storage system of the flash memory, an inappropriate management causes an increase in the cost and cuts the service life of the flash memory short. 
   Referring to  FIGS. 1 ,  2 ,  3 ,  4 ,  5  and  6 , a conventional writing method is shown. As shown in  FIGS. 1 ,  2 ,  3 ,  4 ,  5  and  6 , the manager is ready for writing two pages into the flash memory from page  3  of block  0 , the flash memory will find a new block, block  1 B and defines block  0  as an old block, block  0 A. Next, the page above page  3  of block  0 A to block  1 B is moved, and then the manager writes the page into page  3  and  4  of block  1 B, then moves the page below page  4  of block  0 A to block  1 B, and then erases block  0 A and replaces it by the block  1 B to complete the writing step. 
   However, based on the physical characteristics of the flash memory, damage to the internal structure of the flash memory can easily occur after one million times of erasing steps. Accordingly, for extending the service life of the flash memory, the frequency of the erasing steps must be reduced. As described above, to write data, the flash memory has to locate a new block and erase the old one, in doing so, after one million erasure steps, the flash memory get easily damaged. Accordingly, finding a way to reduce the frequency of erasing steps of the flash memory for extending the service life thereof has become a priority in the field. 
   SUMMARY OF THE INVENTION 
   Accordingly, in the view of the foregoing, the present inventor makes a detailed study of related art to evaluate and consider, and uses years of accumulated experience in this field, and through several experiments, to create a method for reducing the frequency of erasing steps of the flash memory. The present invention provides an innovative, cost effective method for reducing the frequency of erasing steps of the flash memory so that the service life of the flash memory can be substantially promoted. 
   According to an aspect of the present invention, a linking method under a mother and a child block architecture for building a check area and a logic page of the child block is used in order to reduce the frequency of erasing steps of the flash memory and thereby extend the service life of the flash memory and also to promote the processing speed thereof. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     For a more complete understanding of the present invention, reference will now be made to the following detailed description of preferred embodiments taken in conjunction with the following accompanying drawings. 
       FIG. 1  is a flow chart showing a conventional writing method. 
       FIG. 2  is a flow chart showing a conventional writing method. 
       FIG. 3  is a flow chart showing a conventional writing method. 
       FIG. 4  is a flow chart showing a conventional writing method. 
       FIG. 5  is a flow chart showing a conventional writing method. 
       FIG. 6  is a flow chart showing a conventional writing method. 
       FIG. 7  is a flow chart showing a writing method according to a preferred embodiment of the present invention. 
       FIG. 8A  is a flow chart showing a writing method according to a preferred embodiment of the present invention. 
       FIG. 8B  is a flow chart of a check area in the writing method according to a preferred embodiment of the present invention. 
       FIG. 9A  is a flow chart showing a writing method according to a preferred embodiment of the present invention. 
       FIG. 9B  is a flow chart of a check area in the writing method according to a preferred embodiment of the present invention. 
       FIG. 10A  is a flow chart showing a writing method according to a preferred embodiment of the present invention. 
       FIG. 10B  is a flow chart of a check area in the writing method according to a preferred embodiment of the present invention. 
       FIG. 11  is a logic page in the child block according to a preferred embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   Reference will be made in detail to the preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. 
   Referring to  FIG. 7 , a flow chart shows a writing method according a preferred embodiment of the present invention. As shown, the host locates a new block and defines this new block as child block  2  and defines block A as mother block  1 , and then writes into the page  3  and  4  of the block A in the logic page of the flash memory. Next, the host writes data into page  0  of child block  2  (shown in  FIG. 8A ). Meanwhile, the manager marks the first and the second byte in the redundant page  21  of page  0  of child block  2  as C and H respectively to indicate that page  0  belongs to child block  2 . The manager also marks the third byte in the redundant area  21  of page  0  as A× 03  to define that the page  0  of child block  2  is page  3  of mother block  1  for including a check area in page  0  (as shown in  FIG. 8B ). Furthermore, to write data into page  1  of child block  2  (shown in  FIG. 9A ), the manager marks the first and the second byte in the redundant area  22  of page  1  in child block as C and H to indicate that page  1  belongs to child block  2 . The manager also to marks the third byte in the redundant area  22  of page  1  as A× 04  to define that the page  1  of child block  2  is page  4  of mother block  1  for including a check area in page  1  (as shown in  FIG. 9B ). 
   Further, when the host is ready for reading the page in mother block  1  of the logic page, the manager, first of all, reads the child block  2  that corresponds to the mother block  1  in the logic page, whereas the rest of the unmarked pages in child block  2  will be read all from the pages of mother block  1 . 
   Referring to  FIGS. 10A and 10B , a flow chart of the writing method and a flow chart of a check area in the writing method according a preferred embodiment of the present invention are respectively shown. As shown, when the manager writes data into page  3  in mother block  1  of the flash memory, the method of writing is similar to the above-mention procedure. In order to write data in an orderly manner into page  2  of child block  2 , the manager marks the first and the second byte in the redundant page  23  of page  2  of child block  2  as C and H to indicate that page  2  belongs to child block  2 . The manager also marks the third byte in the redundant area  23  of page  2  as A× 03  to define that the page  2  of child block  2  is page  3  of mother block  1  for including a check area in page  2 . 
   And now, in order to differentiate mother block  1  and child block  2 , the check area in the page of child block  2  is examined, the child block  2  obtains marks C and H. In order to analyze whether the data therein is new or old, the check page is examined. Referring to  FIG. 11 , shows a logic page in the child block according to a preferred embodiment of the present invention, wherein the logic page  24  is consisted of checks of every page in child block  2 , and only anterior  6  pages are valid pages and the rest of them are empty (having no data), and page  1  and  4  are both page Y in the logic page, meaning that the manager have written twice to page Y of the logic page and finally page  4  of child block  2  replaces page  1  and becomes the true data in page Y of the logic page. Therefore, the manager needs to read from page  4  of child block  2  for reading page Y in the logic page, as well as to read from page  5  of child block  2  for reading page K in the logic page, and the rest of the pages not being marked in child block  2  are read from the logic page, thus the manager can read out the data easily. 
   If the manager keeps on writing data to a particular page of the block, there is no need for the manager to move all the data to the new block and to erase the old one, accordingly, not only the speed of the writing data can be substantially promoted but also the frequency of the erasing is substantially reduced to increase the service life of the flash memory. 
   While the invention has been described in conjunction with a specific best mode, it is to be understood that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations in which fall within the spirit and scope of the included claims. All matters set forth herein or shown in the accompanying drawings are to be interpreted in an illustrative and non-limiting sense.