Electrical computers and digital processing systems: memory – Address formation – Address mapping
Reexamination Certificate
2001-11-16
2004-03-09
Nguyen, Hiep T. (Department: 2187)
Electrical computers and digital processing systems: memory
Address formation
Address mapping
C711S103000
Reexamination Certificate
active
06704852
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a control device applicable to flash memory cards and, more particularly, to a control device compatible to Smart Media cards, Memory Stick cards, and NAND-gate type flash memories and applicable to various kinds of capacities and a method for building partial lookup table.
BACKGROUND OF THE INVENTION
Along with continual progress of the information industry, high-speed data storage devices (memories) play very important roles due to influence of ever faster CPUs and development of information appliance (IA) products.
As shown in
FIG. 1A
, a data storage device (e.g., a Smart Media card, a Memory Stick card, or a NAND-gate type flash memory)
11
is connected to a host computer
29
mainly via a control device
20
. Of course, the control device
20
can also be built in a subsystem of the host computer
29
. The control device
20
comprises a microprocessor
25
therein, which can be connected to the host computer
29
via an interface controller
24
conforming to the protocol of PCMCIA, IDE, ATA, ATAPI, USB, or their combination. One end of the microprocessor
25
can be connected to the data storage device
11
via a storage control logic circuit
26
. The microprocessor
25
can also be connected to a buffer controller
22
. The buffer controller
22
can temporarily store the data to be accessed by the host computer
29
into a data storage region
21
(a first buffer
211
, a second buffer
213
, and an N-th buffer
219
). Additionally, an ECC logic circuit
23
conforming to the standard of Smart Media is respectively connected to the microprocessor
25
, the buffer controller
22
, and the storage control logic circuit
26
. The ECC logic circuit
22
is controlled by the microprocessor
25
to give a corresponding error-correcting code (ECC) data to a data sector to be accessed. Certainly, the ECC logic circuit
23
is not required if only applied to Memory Stick cards, but a design conforming to serial circuits and CRC of Memory Stick is required. Moreover, the microprocessor
25
can be connected to a lookup table
255
, which can be used to keep logic block addresses (L
0
~L
k-1
) and all physical block address (PBA) values of the corresponding data storage device
11
.
Please refer to FIG.
1
and
FIG. 2
is a diagram with the block as a link unit. DATA and ECC only represent general stored data and the accessory ECC data thereof instead of only a piece of data stored therein. In fact, a block comprises 16 or 32 sectors of data and 16 or 32 sets of ECC data. L represents the data stored in an adjunct region of a block. The data thereof is a pointer built when the system is initiating. When the host computer
29
or the control device
20
is turned on, the microprocessor
25
in the control device
20
will control a scan program to scan all physical blocks (B
0
~B
n-1
) in the memory card
11
to obtain corresponding logic block address data (LBA; L
0
~L
k-1
) of the physical blocks (B
0
~B
n-1
, where k is a little smaller than n). The microprocessor
25
then immediately builds these relations in a lookup table
255
. In other words, the microprocessor
25
will fill the corresponding physical block addresses (Some block in B
0
~B
n-1
, n-k blocks, reserved by system are not mapped with mapping table) of data in the logical block addresses (L
0
~L
k-1
) to build a complete mapping relationship. Therefore, when the host computer
29
is to access a file, it can quickly find the corresponding physical block (B
0
~B
n
) wherein the file is stored to access data.
However, the conventional control device of flash memory cards and the method for fabricating same have the following drawbacks.
1. Data storage devices such as Smart Media cards, Memory Stick cards, or NAND-gate type flash memories utilize a block as a basic unit for erasing or storing data. Along with increase of memory capacity, the number of blocks increases accordingly, but the memory capacity of the lookup table is finite. Therefore, an old data storage device will be not compatible to a new data storage device having a higher capacity because that the new memory card needs a lookup table of a larger capacity.
2. If it is necessary to match flash memory cards of high capacity, the static RAM (random access memory) designed in the control device for storing data of the lookup table needs to choose a higher capacity, hence relatively increasing the cost.
3. When the host computer accesses a file, the control device will search the corresponding data blocks in the whole lookup table to perform access of data. Generally speaking, however, the data blocks corresponding to the file exist in adjacent sectors. Therefore, the operation will waste time and usage ratio of memory capacity of the lookup table.
4. When the host computer accesses a file, the read frequency of system data such as the partition table, the BIOS parameter block (BPB), and the FAT (File allocation table) is higher than that of general files. The capacity of these system data is not large, but it is necessary to search the whole lookup table when reading these system data or the file data each time due to specification limit of the conventional flash memory card, hence lengthening operation time and lowering operation speed.
Accordingly, the present invention aims to propose a novel control device of flash memory cards to resolve the problems in the prior art. The present invention not only can be compatible and applicable to flash memory cards or NAND-gate type flash memories of various kinds of capacities, but also can increase usage ratio of memory of the lookup table and shorten the search time of physical blocks.
SUMMARY OF THE INVENTION
The primary object of the present invention is to provide a control device applicable to flash memory cards and a method for building partial lookup table, wherein a storage memory of a fixed capacity of a lookup table can be applicable and compatible to flash memory cards or NAND-gate type flash memories of various kinds of capacities, thereby achieving unlimited expansion and enhancement of compatibility.
The secondary object of the present invention is to provide a control device applicable to flash memory cards and a method for building partial lookup table, wherein a storage memory of a smaller capacity of a lookup table is utilized to match flash memories of various kinds of specification, thereby controlling the cost.
Another object of the present invention is to provide a control device applicable to flash memory cards and a method for building partial lookup table, wherein a segment lookup table and a FAT accessory lookup table are matched and utilized to relatively enhance operation speed and reduce operation time.
Yet another object of the present invention is to provide a control device applicable to flash memory cards and a method for building partial lookup table, wherein a segment lookup table and a FAT accessory lookup table are matched and utilized to save operation time of the system and relatively enhance usage ratio of memory of the lookup table.
The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing, in which:
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Cheng Tsair-Jinn
Chien Shang Chin
Lai Chen Nan
Lin Chanson
Key Technology Corporation
Nguyen Hiep T.
Rosenberg , Klein & Lee
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