DE4442127A1 - Method for memory management of a flash memory - Google Patents

Description

The invention relates to a method for memory management of Flash memory chips.

From the prior art, in particular in the application for digital answering machine, known as flash memory. On Flash memory is a continuous, linear data memory. In known flash memories of z. B. the company INTEL there a 4 MBit memory, which is divided into seven blocks of different sizes is divided. When saving from the company AMD is a Divided into eight blocks. The flash memory of the Company INTEL can be grouped into four equal blocks become. With these two known flash memories it is only possible to delete in blocks. At a maximum Storage time of z. B. 15 minutes and a subdivision into four blocks this means that per block more than 3 minutes are stored. To delete a whole block, you need to therefore, all the news recorded in these 3 minutes were removed.  

The disadvantage here is that all messages are deleted and in addition, that every rewriting and deleting a block reduces the life of the memory. Most Flash memories have an average lifespan of 100,000 write / erase cycles per block.

It is the object of the invention to provide flash memory management provide a high utilization of the available Storage space is possible.

Another object of the invention is, in addition to the high utilization to provide a flash memory management that is user friendly is.

This is achieved by the teachings of the invention Patent claim 1, the teaching of claim 11, the teaching of Patent claim 12, the teaching of claim 13 and the teaching of claim 17.

The advantage here is that the write / erase cycles in all Blocks find application, so that just the deletion of blocks subject to optimization.

Furthermore, it is advantageous that by optimizing Copy inside the memory the time in which the memory is busy and not described with a new message can, is kept very short.

Further advantageous embodiments of the invention are the Subclaims refer.

In the following the invention will be explained in more detail with reference to FIGS.

The following figures show:

Fig. 1 flow chart of a tuning memory,

Fig. 2 shows a schematic representation of a file,

Fig. 3a Example of moving files

Fig. 3b Example of deleting whole blocks,

Fig. 3c Example of copying files to other blocks,

Fig. 3d Example for the intermediate storage of files.

In the following the invention with reference to FIG. 1 will be explained in more detail.

A flash memory is divided into a number of blocks. These blocks turn into a variety of segments divided. Data in the form of files can, according to the invention to starting from any segment, segment by segment Flash memory to be stored. To delete this corresponding files are marked segment by segment. But can be deleted only in blocks.

As an example, below is a flash memory divided into four blocks. Another possibility is also to divide a flash memory in eight blocks or even in sixteen blocks. This depends on the respective semiconductor manufacturer. In the example selected here with four blocks, a current filling level of the flash memory is determined in a first step 1 . This is done by determining the number of unoccupied, occupied deletion marked and occupied unmarked segments of each block. The degree of filling of the individual block and the filling level of the entire flash memory cause memory to be optimized after a threshold has been exceeded. In this case, the threshold may be an empirically determined value, the z. B. front adjustable. It is also conceivable, depending on the degree of filling different, ie variable thresholds pretend.

If the filling level of the memory is above the threshold, there is a requirement to optimize the memory 2 . This can be done in accordance with an embodiment of the invention by moving occupied unmarked files in the direction of each unoccupied end of the memory. The selected files remaining in the original block are deleted block by block. In the event that a displacement of the files is not possible, it can be determined in a further step 4 whether a whole block exists in which there are no occupied unmarked segments. The whole block is then deleted.

In the event that there is no block in the flash memory which is completely erasable, the block in which there is the smallest number of occupied, unmarked segments is determined. These occupied unmarked segments associated with a file are then copied 5 to unused areas of other blocks 5 . The previously determined block is then deleted. For the present case, it is assumed that the file which is being copied completely fits into the unoccupied area, ie remains together as a whole.

In the event that there is no possibility to copy segments into unoccupied areas of other blocks, in a next step 6 again the block is determined in which there is the smallest number of occupied unmarked segments, whereupon these segments of the determined block are in a marked one Cached area of another block. Thereafter, the previously determined block is deleted as a whole and the cached data are written back into the now completely empty block.

In the event that, according to the invention, one of these four steps 3, 4, 5, 6 is executed for memory optimization, the degree of filling is again determined and a threshold value comparison is carried out 1 .

In the event that none of these previous steps is performed, so an optimization is not possible, in a further step 7, a user query will be made. Here, the user is asked for the files that are to be marked in addition to the deletion. If the user gives a positive response to this, that is to say, erasable files, then again step 1 can be continued. In the event that the user does not wish to delete another segment, an abort and no new file is stored.

In the following, the schematic representation of a file is explained with reference to FIG. 2, which is a plurality of segments long. At the beginning of each file I is a file header 00000, this is for example filled with zeros. The second II is at the beginning of each file, a segment header, z. B. 10000. At the beginning of the second segment, which still counts to the file, there is twice a segment start label 10000. This is done for each additional segment of the file in this form. For the beginning of a new file I, a new file header 00000 is again provided. It is therefore clear how long an existing file is.

Furthermore, there is the beginning of a file in another Area III z. For example, the total length of the existing file is up to their end. Optionally, additionally date, year and Time of entry of the file to be entered. After that will be  the data to be stored in the remaining area or in the stored remaining areas. Thus, it is clear determines which segments are occupied. To mark for deletion a file is z. B. in all segment preambles II likewise no zero registered, thus 00000. Thus stands clear determines that the data still stored therein is for deletion ready. In the segment preamble II can by a Code can be defined which form of data is stored therein are. For example, PCM data or ADPCM data, etc., what by a code 01000 or 00100 is specified.

In the following will be (without drawing) a program module for the Operating a flash memory explained. The flash memory is also divided into blocks, which in turn into a variety are divided by segments. It will also be a legal one Filling level of the flash memory determined, which is also from the Number of unoccupied, out of the number of occupied and to Delete selected segments and from the number of occupied unmarked segments of each block. A Memory optimization is then by means of the following control commands performed. By means of a control command is caused by Move files occupied segments, and by means of a Another control command is a block with the remaining occupied segments deleted for deletion. In the case, that this is not executable, a block is determined in which there are no occupied, unmarked segments and caused by a control command, then the whole block deleted. If this is also not possible, the block becomes determined, in which occupied the smallest number of unmarked segments is located.

These are then, caused by another control command, in Cached segments of other blocks are cached. The block will be deleted and after deleting the  cached segments reconstructed again in the block. In the event that this is also not possible, the Block, in which the smallest number of occupied, unmarked segments is located. This is then initiated by a control command, a copying of the occupied, unmarked segments made. But this only happens when copying an entire file to a free space can be. Again, in the event that none of these Optimizations is possible with another control command User prompt causes the user to be deleted Additionally, you can mark files.

A broad use of such program modules is, for example for storing voice messages in answering machines conceivable. For example, with one used here Flash memory a variety of messages are stored to z. B. a duration of 15 minutes in total. Often exists the desire to delete messages and other messages to keep for a longer period of time.

In the following an embodiment will be explained in more detail with reference to FIG. 3a. In the example chosen here, the flash memory has four blocks A, B, C, D. Marked areas of segments that are ready to be erased are indicated by the short vertical stitches (||||). Segments that are not marked, that is, should continue to be saved, should be identified by the long horizontal bar. The sequence of files of the same kind can be evaluated according to the invention by evaluating additional information that is at the beginning of the first segment of a file (such as date, time).

In the first block A 5 different files are stored 1, 2, 3, 4, 5. In the second block B is only the end of the fifth file 5. Should now z. For example, if files 2 and 4 are marked for deletion (see Figures 3a, 2 ', 4'), then file 3 becomes file 2 and file 5 becomes file 3. In the case of files Δt, the unmarked files 1, 2, 3 are moved to the end of the memory in the fourth block D. The marking of the files is changed, as already explained. 5 becomes 3, 3 becomes 2 and 1 remains. Thus, the files 1, 2, 3 are after being moved, seen from the rear, in the order of 3, 2, 1 in the last block D. The marked files in the first block A are now deleted in this block. Thus, three free blocks are available for re-storage A, B and C. New messages in the form of files are now rewritten in the block A.

In the following, the erase of entire blocks will be explained with reference to FIG. 3b. There are several files. In block A there are five files 2, 3, 4, 5, 6. Of these, file 3 is marked for deletion (3 '). In block B there are two files 5 and 1, both marked for deletion (5 ', 1'). Otherwise the block is not occupied. Block C is also not occupied. In block D there are files 7, 8 which are to be kept. It will now be noted that block B is erasable. For deleting z. B. the blank part of the block are also marked, whereupon then the block is deleted. Following Δt there are only data in blocks A and D. Here, 2 in 1, 4 in 2, 6 in 3, 7 in 4 and 8 in 5 has been changed. Blocks B and C are free.

In the following, the copying of files into other blocks is explained with reference to FIG. 3c. It is determined which block has the least number of occupied, unmarked segments. In this case, this is block C. The file 7 therein, which is not marked, is copied to the free area of block B (now 4, after renumbering). The remaining area in C is marked for deletion, and thus (Δt) the area is completely free again.

In the following, an example of the intermediate storage of files is explained with reference to FIG. 3d.

In the present case, the block is also determined, in which occupied the least number of unmarked Located segments. Here's the block C. It's trying the file 5 (after renumbering), which is not marked, to the Delete the block to be able to execute, outsource. It exists no more blank area where the file will be repackaged can. Therefore, the file 5 is tried in the area of the Delete cached file 2 to cache. This is not enough off, and so the remaining part of the file z. In block B, in the blank (between 3 and 5 '), but also in the marked one Area 5 'cached. After that, the block is deleted. Thereafter (Δt), the file 5 is in the now "empty" block reconstructed.

The enumeration of the cases mentioned here is only an example and makes no claim to completeness.

In the following the invention according to claim 13 using the following example explained.

The fill level of the flash memory, which is divided into four blocks is determined by the number of unoccupied the number the occupied, marked for deletion and the occupied, not marked segments of each of the four blocks is determined.  

If the degree of filling exceeds a threshold, the block is determined in which the least number of occupied, unmarked Located segments.

In a further step, the occupied, unmarked Segments linked to segments marked for deletion to be overwritten further blocks.

This preparation is explained below using an example, in which any data was selected. It was based on that especially for speech data, an equal distribution of 0 and 1 occurs.

In the other block are marked for deletion Segments, which means that there is still data in the segments are inscribed. Accordingly, this data can be exemplary specify, in hexadecimal and dual Presentation:

HEX DUAL 8 3 1000 0011 0 2 0000 0010 0 0 0000 0000 B A 1011 1010 5 7 0101 0111 1 A 0001 1010 0 F 0000 1111 E D 1110 1101 2 2 0010 0010 D 5 1101 0101 D 2 1101 0010 · · · · · ·

The data of the occupied, unmarked segment are for example:

HEX DUAL 1 5 0001 0101

This data should be overwritten.

The following is the data of the data marked for deletion by means of a logical link, z. B. AND, with the occupied linked to unmarked data.

This results in the linked data

Thus, the data is not completely overwritten yet 0000 0001 is not or only partially 0001 0101. Accordingly, further links become necessary until for complete overwriting.

It follows that the following data, which is in the for Delete marked segment, re-link, here also AND, is applied.

It follows:

This does not contribute.

And further

It follows:

And further

It follows:

This provides a contribution, but also corresponds with the Equations I, II and III are not yet the full data of 0001 0101.  

And further

It follows:

The following is a tabular overview of the given previously overwritten data. This is in the left Column the data to be overwritten, and in the middle Column the data that has been overwritten by the link. The two right-hand columns give the corresponding hexadecimal Numbers, with the rightmost column to be encoded Data indicates.

In the equation (V), the logical operation gives a 15 0001 0101.

Table 3

But since already a 0 1 0000 0001 with the equation (I) and a 1 0 0001 0000 was overwritten by equation (V), is here with the equation (V) only a 0 4 0000 0100 programmed. The number of the equation (V) is here by a logical OR or determined by subtraction.

Furthermore, it follows that an end criterion can be determined must to specify that the overwriting is completed.

An end criterion could look like this: The as in advance explained logical association with the following for deletion marked data gives:

It follows:

If one compares this with the values entered in Table 5, it is found that equation (VI) of equation (IV) equivalent. Accordingly, it is stated that at least a bit position is again a 1, which is the final criterion serves.

Another example arises when the occupied ones do not For example, tagged dates are:

HEX DUAL 0 0 0000 0000

The ones marked for deletion are, for example:

HEX DUAL 0 F 0000 1111 E D 1110 1101 · · · · · ·

In the link that corresponds to the one explained above, each would Link with 00 to 00 lead. For this reason, that must End criterion to be extended.

It should be noted that:

Table 6

At the bit positions 0, 2 and 3 of the data of the middle column is in each case a 1. Accordingly, it is determined that if more than one bit position contains a 1 at least twice, this one byte represents 0 and thus the end criterion sets.

Another example is the following, marked for deletion Data (see Tab. 7) and the occupied, unmarked data given (Table 8).

HEX DUAL 2 2 0010 0010 D 5 1101 0101 D 2 1101 0010 · · · · · ·

HEX DUAL 0 0 0000 0000

The following table shows the results of the logical link:

Table 9

The dual values of equations (VII) and (VIII) have none matching bit position with 1, with the result that no End criterion is met. The comparison of equation (IX) with Equation (VIII), however, shows again matching Bit positions, from which in turn an end criterion is fulfilled.  

In summary, the data from Tab. 1 after the Overwrite:

Table 10

The unmarked data overwritten as explained above are preferably after the block has been deleted reconstructed. The deletion creates new freer Memory space and language can be recorded again.

Claims (19)

A method of operating a flash memory, which is divided into blocks, and whose blocks are divided into a plurality of segments, in which

• - data in the form of files with an arbitrary segment, beginning segment by segment, are stored and files corresponding to the deletion are marked segment by segment,
• - A current filling level of the flash memory is determined ( 1 ) by the number of occupied and marked for deletion, the occupied, unmarked and unoccupied segments of each block is determined, and
• - After exceeding a threshold of the degree of filling, a memory optimization ( 2 ) is made.

2. The method and claim 1, in which occupied for memory optimization, unmarked files in the direction of each unoccupied end of the flash memory are moved ( 3 ), and the remaining files in the blocks, marked files are deleted block by block. 3. The method of claim 1 or 2, wherein it is determined for memory optimization, if a block exists in which there are no occupied, unmarked segments ( 4 ) and this is then deleted. 4. The method according to any one of claims 1 to 3, wherein the memory for optimizing the block is determined in which there is the smallest number of occupied, unmarked segments and these are then copied to unoccupied areas of other blocks ( 5 ) and then the previously determined block can be deleted. 5. The method according to any one of claims 1 to 4, wherein the memory for optimizing the block is determined in which there is the smallest number of occupied, unlabeled segments and these segments are cached in a marked area of another block ( 6 ), the previously determined block is deleted, wherein then the cached data are reconstructed. 6. The method according to any one of claims 1 to 5, wherein, if after the threshold of the filling level no memory optimization is feasible, a user query takes place ( 7 ), in which the user can specify the files to be marked in addition to the deletion , 7. The method according to any one of claims 1 to 6, wherein in the beginning Each file has a preamble (I) and a Segment Header (II) is defined and where in each further associated segment two segment starting labels are defined.   8. The method of claim 7, wherein the preamble with Zeros is filled, and over the occupation of the Segment preambles the type of data stored is marked. 9. The method of claim 8, wherein the marked segments with Zeroes in the segment preambles. 10. The method of claim 1, wherein for the marking of Files of the same kind Additional information at the beginning of the first Segments of a file have been inserted. 11. Program module for operating a flash memory, which is divided into blocks, and whose blocks are divided into a plurality of segments, wherein a permissible degree of filling of the flash memory, which consisted of the number of unoccupied, occupied and for deletion marked segments and occupied, unmarked segments of each block is determined, and a memory optimization is then made by means of control commands in which is caused by a control command to move files occupied by files and occupied in the remaining by means of a control command, for deletion marked segments are deleted, or
by determining a block in which there are no occupied and unmarked segments, which is then cleared, caused by a control command, or
by determining the block in which there is the smallest number of occupied, unmarked segments, which are then copied, by a control command, into unoccupied segments of other blocks, or
by determining the block in which there is the smallest number of occupied, unmarked segments, which are then latched in marked segments of other blocks, prompted by a control command, and then reconstructed after clearing the determined block, or
by another control command causing a user query in which the user can mark files to be deleted. 12. Use of the program module according to claim 11 for storage of voice messages, especially in an answering machine. 13. A method of operating a flash memory, which is divided into blocks and whose blocks are divided into a plurality of segments, in which

• - after exceeding a threshold of a degree of filling determined by the number of occupied and marked for deletion, occupied, unmarked and unoccupied segments of each block, the block in which the smallest number occupied, unmarked segments,
• - and the occupied, unmarked segments of this block are overwritten by linking to segments marked for deletion of another block,
• - and then the previously determined block can be deleted.

14. The method according to claim 13, wherein the linking takes place, in that a logical AND between data of the occupied, unmarked segments and data in the for deleting marked segments is made.   15. The method of claim 13, wherein the linkage such takes place that a logical OR between data of the occupied, unmarked segments and data in the for deleting marked segments is made. 16. The method according to any one of claims 14 or 15, wherein at least one more logical connection of the data of the occupied, unmarked segments with data of at least one other segments marked for deletion until the fulfillment of one Final criterion is made. 17. The method of claim 16, wherein the end criterion from this determines that in a segment in a bit position the Repetition of at least one bit value occurs. 18. The method according to any one of claims 13 to 17, wherein the overwritten data of the other block in the previously determined, deleted block to be reconstructed again. 19. Program module for operating a flash memory, which is divided into blocks, and whose blocks are divided into a plurality of segments, wherein a permissible degree of filling of the flash memory, which consisted of the number of unoccupied occupied and for deletion memory segments and occupied, unmarked segments of each block is determined, and a memory optimization is then made by means of control commands in which is caused by a control command to move files occupied by files and occupied in the remaining by means of a control command, for deletion marked segments are deleted, or
by determining a block in which there are no occupied and unmarked segments, which is then cleared, caused by a control command, or
by determining the block in which there is the smallest number of occupied, unmarked segments, which are then copied, caused by a control command, into unoccupied segments of other blocks, or
by determining the block in which there is the smallest number of occupied, unmarked segments, which are then latched in marked segments of other blocks, prompted by a control command, and then reconstructed after clearing the determined block, or
by determining the block in which there is the smallest number of occupied, unmarked segments which are then overwritten in a linked form to data in segments of another block marked for deletion and / or
by another control command causing a user query in which the user can mark files to be deleted.