MANAGEMENT METHOD FOR REDUCING UTILIZATION RATE OF RANDOM ACCESS MEMORY (RAM) USED IN FLASH MEMORY

• US 20080162793A1
• Filed: 12/20/2007
• Published: 07/03/2008
• Est. Priority Date: 12/28/2006
• Status: Active Grant

• Current Assignee: Genesys Logic Incorporated
• Original Assignee: Genesys Logic Incorporated
• Inventors: Hsieh, Jen-wei, Chang, Yuan-hao, Chu, Yuan-sheng, Kuo, Tei-wei, Yang, Cheng-chih
• Granted Patent: US 8,392,690 B2
• Time in Patent Office: Days
• US Class Current: 711/103
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory

Abstract

A management method for reducing the utilization rate of random access memory (RAM) while reading data from or writing data to the flash memory is disclosed. A physical memory set is constructed from a plurality of physical memory blocks in the flash memory. A logical set is constructed from a plurality of logical blocks wherein the data stored in the logical set are stored in the physical memory set. Further, the data stored in each of the logical blocks are stored in one number of physical memory blocks. A mapping table is constructed and includes a hash function, a logical set table, a physical memory set table, and a set status table for managing the relationship among the physical memory sets, physical memory blocks, and logical blocks while reading data from or writing data to the flash memory. Further, the management method operates and maintains the physical memory sets, the physical memory blocks, and the logical blocks at a set level so that the utilization rate of random access memory is reduced to decrease the access capacity of the random access memory while operating the physical memory blocks and the logical blocks of the flash memory.

Claims

1. A management method for reducing the utilization rate of random access memory (RAM) utilized in flash memory, the method comprising the steps of:

(a) constructing a physical memory set from a plurality of physical memory blocks in the flash memory;

(b) constructing a logical set from a plurality of logical blocks wherein the data stored in the logical set are stored in the physical memory set during the step (a), and the data stored in each of the logical blocks are stored in one number of physical memory blocks;

(c) defining a data-accessing table which is located between the logical block and the physical memory set and defining a mapping table which is located between the physical memory set and the logical blocks during the step (b), wherein the mapping table comprises a hash function, a logical set table, a physical memory set table, and a set status table;

(d) determining whether the data are either read from or written to the flash memory, wherein if the data are read from the flash memory, proceed to step (f), and if the data are written to flash memory, proceed to step (g);

(e) writing the data to the flash memory and updating the mapping table, wherein the data are written to the flash memory and the mapping table is updated based on the relationship of the mapping table between the physical memory set and the logical blocks; and

(f) reading an index of the data, wherein the data stored in the flash memory are read based on the relationship of the mapping table between the physical memory set and the logical blocks.

2. The method of claim 1, wherein the hash function of the mapping table in step (d) is a divider.

3. The method of claim 2, wherein a quotient of the hash function is a logical set number, and a remainder of the hash function is an inter-set number.

4. The method of claim 1, during the step (e), further comprising the steps of:

(e1) issuing an access command for accessing the flash memory by a host and assigning a logical block address, wherein the host issues the access command and writes the accessed data to at least one of the logical blocks;

(e2) inquiring the mapping table for identifying the physical memory set based on the logical block address during the step (e1);

(e3) determining whether unused physical memory blocks are located in the physical memory set, wherein if yes, proceed to step (e4), and if no, proceed step (e31);

(e31) searching at least one unused physical memory set;

(e32) copying the effective data of the physical memory block in the physical memory set to the unused physical memory set during the step (e31), and releasing the physical memory set;

(e4) acquiring at least one unused physical memory block in the physical memory set during the step either (e32) or (e2);

(e5) writing the data to the physical memory block for recording the data to unused one of the physical memory blocks during the step (e4); and

(e6) updating the mapping table for renewing the hash function, the logical set table, the physical memory set table, and the set status table of the mapping table.

5. The method of claim 4, during the step (e6), further comprising the steps of:

(e61) issuing an access command for accessing the flash memory by the host and writing the data to an assigned logical block address, or updating the data, stored in the logical block address;

(e62) operating the logical block address for generating the logical set number and the inter-set number by the hash function;

(e63) inquiring the logical set table in the random access memory (RAM) based on the logical set number for generating the physical memory set number corresponding to the logical block address;

(e64) inquiring the physical memory set table based on the physical memory set number for generating the set status index of the physical memory set;

(e65) inquiring the invariant set status table based on the set status index for generating the status presentation sequence of the physical memory set;

(e66) determining whether at least one unused physical memory block is located in the physical memory sets, wherein if no, proceed to step (e67), and if yes, proceed step (e70);

(e67) searching one unused physical memory set;

(e68) copying the effective data of the physical memory block in the physical memory set to the unused physical memory set, releasing the physical memory set, and updating the logical set table and the physical memory set table;

(e69) searching unused one of the physical memory blocks in the unused physical memory set;

(e70) writing the new data to the unused one of the physical memory blocks;

(e71) constructing a status presentation sequence based on the updated set status; and

(e72) updating the physical memory set table.

6. The method of claim 1, during the step (f), further comprising the steps of

(f1) issuing an access command by a host to access the flash memory and reading the data from an assigned logical block address;

(f2) operating the logical block address by a hash function for generating the logical set number and the inter-set number;

(f3) inquiring the logical set table in the random access memory (RAM) based on the logical set number during the step (f2) for generating the physical memory set number corresponding to the logical block address;

(f4) inquiring the physical memory set table based on the physical memory set number during the step (f3) for generating the set status index of the physical memory set;

(f5) inquiring the invariant set status table based on the set status index during the step (f4) for generating the status presentation sequence of the physical memory set;

(f6) searching the status presentation sequence to determine whether at least one value of the status presentation element in the status presentation sequence is the same as the inter-set number in the sets, wherein if yes, proceed step (f7), and if no, proceed to the step (61);

(f61) reporting errors or returning the data size of an empty block, and proceeding to end; and

(f7) reading the data on the block “

i-th” and

returning the data if the value in the status presentation element “

i-th”

is the same as the inter-set number.