JP3913128B2 - Memory card - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a memory card, and more particularly to a memory card that downloads program data and stores it in a nonvolatile memory.
[0002]
[Background Art and Problems to be Solved by the Invention]
Memory cards are used for writing / reading information in digital devices such as digital cameras, PDAs, portable audio devices, cellular phones, and personal computers. The memory card has two chips, a flash memory and a controller. In recent years, the flash memory mounted on a memory card is increasing in capacity, and accordingly, large-scale data can be stored in the flash memory. However, at present, memory cards only exchange data with digital devices. There are IC cards that can download and execute application programs. However, the capacity of the nonvolatile memory for storing the program is very small compared to the capacity of the flash memory mounted on the memory card.
[0003]
An object of the present invention is to provide a memory card capable of reducing the circuit scale.
[0004]
[Means for Solving the Problems and Effects of the Invention]
The memory card according to the present invention includes a first nonvolatile memory, a second nonvolatile memory, and a separation unit. The first nonvolatile memory has a predetermined erase unit. The second nonvolatile memory has an erase unit larger than the erase unit of the first nonvolatile memory. The separation unit separates at least a portion of the program data downloaded to the memory card that may be rewritten, stores the separated portion in the first nonvolatile memory, and stores the remaining portion in the second nonvolatile memory Stored in the memory.
[0005]
In the memory card, in the execution process of the downloaded program, the rewriting process of data in the program does not occur in the second nonvolatile memory but occurs only in the first nonvolatile memory. As described above, the rewriting process of variables or the like is performed in the first non-volatile memory with a small erase unit, so that the required buffer size is smaller than when processing is performed in the second non-volatile memory with a large erase unit. The circuit scale can be reduced.
[0006]
In addition, the size of data temporarily buffered for rewriting is smaller in the first nonvolatile memory than in the second nonvolatile memory. Accordingly, the buffering processing time for rewriting can be reduced compared with the case where the rewriting processing is performed in the second nonvolatile memory, and the processing time required for rewriting can be reduced.
[0007]
Further, since the downloaded program data is stored separately in the first nonvolatile memory and the second nonvolatile memory, the security is improved.
[0008]
Preferably, the program data includes a function and a variable. The separation unit stores the function in a second non-volatile memory, stores in the first non-volatile memory one of the variables that may be rewritten, and rewrites the variable. What is not possible is stored in the second non-volatile memory.
[0009]
Preferably, the program data is a class described in an object-oriented programming language. The separation unit stores the class variable in the first nonvolatile memory, and stores the class method in the second nonvolatile memory.
[0010]
Preferably, the program data is a class described in an object-oriented programming language. The separation unit stores, in the first nonvolatile memory, variables of the class that are likely to be rewritten, and those of the class that are not likely to be rewritten and of the class Store the method in the second non-volatile memory.
[0011]
Preferably, the memory card further includes an encryption processing unit. The encryption processing unit encrypts the remaining portion to be stored in the second nonvolatile memory. The first nonvolatile memory, the separation unit, and the encryption processing unit are formed on the same chip.
[0012]
In the memory card, since the program data stored in the second nonvolatile memory is encrypted by the encryption processing unit, the security is further improved.
[0013]
Preferably, the first nonvolatile memory is an EEPROM, and the second nonvolatile memory is a flash memory.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.
[0015]
<Overall configuration of memory card system>
FIG. 1 is a block diagram showing an overall configuration of a memory card system according to an embodiment of the present invention. In the system shown in FIG. 1, a memory card 1 is inserted into a slot (not shown) of a digital device 2 (for example, a digital camera, a PDA, a portable audio device, a mobile phone, a personal computer, etc.). Program data is downloaded. The downloaded program is executed inside the memory card 1.
[0016]
<Digital equipment 2>
The digital device 2 converts (compiles) source code described in Java (TM), which is an object-oriented programming language, into byte code and transfers it to the memory card 1.
[0017]
<Memory card 1>
The memory card 1 includes a controller chip 100 and a flash memory chip 200.
[0018]
The controller chip 100 includes interfaces 110, 140 and 180, a CPU 120, a virtual machine 130, an EEPROM 150, buffer RAMs 145 and 160, and an encryption processing unit 170.
[0019]
The interface 110 is an interface between the digital device 2 and the controller chip 100. The interface 110 transfers the class file (byte code) downloaded from the digital device 2 to the virtual machine 130.
[0020]
The virtual machine 130 separates the static variable from the class file given from the interface 110 and supplies the static variable to the interface 140, and supplies the rest (the applet code and the static final variable) to the buffer RAM 160. The virtual machine 130 converts the program data (byte code) read from the EEPROM 150 and the flash memory chip 200 into a format that can be executed by the CPU 120 by an interpreter method.
[0021]
The CPU 120 executes the program converted by the virtual machine 130. The CPU 120 controls the operation of the controller chip 100.
[0022]
The interface 140 is an interface between the virtual machine 130 and the CPU 120, the EEPROM 150, and the buffer RAM 145. The interface 140 transfers the static variable from the virtual machine 130 to the EEPROM 150 via the buffer RAM 145.
[0023]
The buffer RAM 145 buffers data to be transferred to the EEPROM 150 and data output from the EEPROM 150. The buffer RAM 145 temporarily buffers the data when the data recorded in the EEPROM 150 is rewritten.
[0024]
The EEPROM 150 stores a static variable from the interface 140. The EEPROM 150 is a non-volatile memory that erases data in units of words.
[0025]
The buffer RAM 160 temporarily stores the applet code and the static final variable from the virtual machine 130. The buffer RAM 160 temporarily stores program data read from the flash memory 200 and decrypted by the encryption processing unit 170.
[0026]
The encryption processing unit 170 encrypts the program data (apple code and static final variable) stored in the buffer RAM 160 and supplies it to the interface 180. The encryption processing unit 170 decrypts the program data read from the flash memory chip 200.
[0027]
The interface 180 is an interface between the controller chip 100 and the flash memory chip 200. The interface 180 transfers the program data (apple code and static final variable) encrypted by the encryption processing unit 170 to the flash memory chip 200. The interface 180 transfers the program data read from the flash memory chip 200 to the encryption processing unit 170.
[0028]
The flash memory chip 200 stores encrypted program data (apple code and static final variable) from the interface 180. The flash memory chip 200 is a nonvolatile memory that erases data in block units or chip units. That is, the erase unit of the flash memory chip 200 is larger than the erase unit of the EEPROM 150.
[0029]
<Download the program>
Next, downloading of program data from the digital device 2 to the memory card 1 in the memory card system shown in FIG. 1 will be described.
[0030]
Here, the program data of the source code as shown in FIG. 2 is downloaded. The source code shown in FIG. 2 is an application program for using the memory card 1 as a point card, and is written in Java (TM). In this program, points are added at different point return rates for each purchased item (food, clothing, electrical appliances). The point balance is recorded for each purchased item. Since the point balance is updated every time a product is purchased, it is declared as a static variable. On the other hand, since the point reduction rate remains unchanged from the initial setting value, it is declared as a static final variable.
[0031]
The source code described in Java (TM) is converted (compiled) into byte code and downloaded from the digital device 2 to the memory card 1. The byte code (class file) downloaded to the memory card 1 is separated in the virtual machine 130 into a static variable portion, an Applet code, and a static final variable portion. The Apple code and the static final variable part are stored in the flash memory 200, and the static variable part is stored in the EEPROM 150. In this way, a portion where rewriting may occur (static variable portion) is stored in the EEPROM 150, and a portion where rewriting does not occur (Apple code and static final variable portion) is performed by the encryption processing unit 170. After being encrypted, it is stored in the flash memory 200. In an IC card that can download and execute an application program, as shown in FIG. 2, all downloaded byte codes (class files) are stored in an internal EEPROM without being separated.
[0032]
Next, the separation process performed in the virtual memory 130 will be specifically described with reference to FIG.
[0033]
The class file downloaded from the digital device 2 to the memory card 1 includes an applet code part (method), a static final variable, and a static variable. The first byte of the applet code part is 0x01. The first byte of the static final variable is 0x02. The first byte of the static variable is 0x03. As described above, in the class file compiled in the digital device 2, the applet code portion, the static final variable, and the static variable can be identified by determining the first one byte. This determination is performed by the address analysis unit 131 of the virtual machine 130.
[0034]
The storage unit 132 stores program data in the flash memory 200 or the EEPROM 150 according to the determination result of the address analysis unit 131. When it is determined that the first byte is 0x01, the program data (applet code part) is stored in the flash memory 200. When it is determined that the first byte is 0x02, the program data (static final variable) is stored in the flash memory 200 (after being encrypted by the encryption processing unit 170). When it is determined that the first byte is 0x03, the program data (static variable) is stored in the EEPROM 150.
[0035]
As a result of the above processing, as shown in FIG. 4, the applet code and the static final variable are stored in the flash memory 200, and the static variable is stored in the EEPROM 150.
[0036]
<Execution of downloaded program>
Next, an execution process of a program stored separately in the flash memory 200 and the EEPROM 150 will be described. The process executed here is a process having the contents shown in the source code of FIG. Hereinafter, a description will be given with reference to FIGS. 5B and 5C.
[0037]
When the purchase amount (value) and the index (i) indicating the item type are input to the CPU 120, the virtual machine 130 fetches the “instruction” stored in the applet code part (addPoint) on the flash memory 200, In the interpreter unit, the CPU 120 converts the data into an executable format by the interpreter method. The converted instruction is executed by the CPU 120. In this way, the following processing is performed.
[0038]
<Step ST51>
_Balload ... Acquires the i-th data (kangenritu [i]) of the kangenrit array on the flash memory 200 (X).
[0039]
<Step ST52>
_Mul... Multiplying Value and kangenritu [i].
[0040]
<Step ST53>
_Balload ... Acquires the i-th data (point [i]) in the point array on the EEPROM 150 (Y).
[0041]
<Step ST54>
_Add: The result of the multiplication process in step ST52 and the point [i] acquired in step ST53 are added.
[0042]
<Step ST55>
_Basto ... The result of the addition process in step ST54 is stored in point [i] on the EEPROM 150 (Z). That is, the content of point [i] is rewritten.
[0043]
<Effect>
In the current technology, the storage capacity of the EEPROM is much smaller than that of the flash memory. For this reason, in the case of a large-scale program, it is necessary to store it in a flash memory.
[0044]
Normally, when a program is executed, processing for rewriting small data (such as variables) in the program occurs. When executing a program stored in the flash memory, this rewriting process is performed in units of erase. However, the erase unit of flash memory is very large compared to the erase unit of EEPROM. For this reason, when executing a program stored in the flash memory, a huge buffer memory is required for rewriting variables.
[0045]
For example,
Storage capacity: 512Mbit
Program unit: 512 bytes = 1 page
Erase unit: 32 pages
In the case of the NAND type flash memory, a 16 kbyte buffer RAM is required.
[0046]
In the memory card system according to the embodiment of the present invention, a portion (static variable) of program data (class file) downloaded from the digital device 2 to the memory card 1 that may be rewritten is stored in the EEPROM 150 and rewritten. A portion (Applet code and static final variable) in which there is no possibility of occurrence is stored in the flash memory 200. Therefore, the data rewriting process in the program does not occur in the flash memory 200 but only occurs in the EEPROM 150. As described above, since the variables 150 are rewritten in the EEPROM 150 having a small erase unit, the capacity of the buffer memory (buffer RAM 145) necessary for the rewrite process is smaller than in the case of performing the process in the flash memory 200 having a large erase unit. As a result, the circuit scale can be reduced. The size of data temporarily buffered for rewriting is smaller in the EEPROM 150 than in the flash memory 200. Therefore, the buffering processing time for rewriting can be shortened compared with the case of performing rewriting processing in the flash memory 200, and the processing time required for rewriting can be shortened.
[0047]
Further, since the program data downloaded to the memory card 1 is stored separately in the flash memory 200 and the EEPROM 150, the security is improved. Since the program data stored in the flash memory chip 200 is encrypted by the encryption processing unit 170, the security is further improved.
[0048]
Further, when accessing program data stored in the EEPROM 150, it is not necessary to perform encryption / decryption processing, so that the processing time is improved.
[0049]
Here, the static variable is stored in the EEPROM 150 and the Applet code and the static final variable are stored in the flash memory 200. However, the static variable and the static final variable are stored in the EEPROM 150, and the Applet code is stored in the flash memory 200. May be.
[0050]
If the time required for reading from the flash memory 200 and the decrypting process by the encryption processing unit 170 is longer than the time required for reading from the EEPROM 150, the CPU 120 controls the EEPROM 150 to store a part where the flash memory 200 is frequently accessed. You may write.
[0051]
Further, the buffer RAM 145 and the buffer RAM 160 are configured as a common RAM, and this RAM is operated as a buffer RAM for the EEPROM 150 when the EEPROM 150 is operated, and is operated as a buffer RAM for the flash memory 200 when the flash memory 200 is operated. May be. Thereby, the circuit area required for the RAM can be reduced, and the circuit scale can be reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an overall configuration of a memory card system according to an embodiment of the present invention.
FIG. 2 is a diagram showing how program data downloaded from a digital device is stored in a memory card.
FIG. 3 is a diagram illustrating how program data downloaded from a digital device is stored in a memory card.
FIG. 4 is a diagram showing program data stored in a flash memory and an EEPROM.
FIGS. 5A to 5C are diagrams for explaining a program execution procedure; FIG.
[Explanation of symbols]
1 memory card, 100 controller chip, 200 flash memory chip (second non-volatile memory), 130 virtual machine (separating unit), 150 EEPROM (first non-volatile memory), 170 cryptographic processing unit.

Claims (5)

A memory card,
A first non-volatile memory having a predetermined erase unit;
A second nonvolatile memory having an erase unit larger than the erase unit of the first nonvolatile memory;
Of the program data downloaded to the memory card, at least a portion that may be rewritten is separated, the separated portion is stored in the first nonvolatile memory, and the remaining portion is stored in the second nonvolatile memory. A separation unit for storing in the memory,
The program data is composed of a function and a variable, each of which is assigned an identification code, and the variable is identified as one that may be rewritten or one that may not be rewritten. A code is given,
The separation unit is
The identification code is determined, the function is stored in the second non-volatile memory, and the variable that may be rewritten is stored in the first non-volatile memory. A memory card characterized in that a memory card that is unlikely to be rewritten is stored in the second nonvolatile memory. A memory card,
A first non-volatile memory having a predetermined erase unit;
A second nonvolatile memory having an erase unit larger than the erase unit of the first nonvolatile memory;
Of the program data downloaded to the memory card, at least a portion that may be rewritten is separated, the separated portion is stored in the first nonvolatile memory, and the remaining portion is stored in the second nonvolatile memory. A separation unit for storing in the memory,
The program data is a class described in an object-oriented programming language, and an identification code is assigned in advance to each of the variables and methods of the class,
The separation unit is
A memory card comprising: discriminating the identification code; storing the class variable in the first nonvolatile memory; and storing the class method in the second nonvolatile memory. A memory card,
A first non-volatile memory having a predetermined erase unit;
A second nonvolatile memory having an erase unit larger than the erase unit of the first nonvolatile memory;
Of the program data downloaded to the memory card, at least a portion that may be rewritten is separated, the separated portion is stored in the first nonvolatile memory, and the remaining portion is stored in the second nonvolatile memory. A separation unit for storing in the memory,
The program data is a class described in an object-oriented programming language, and an identification code is assigned in advance to each of the variables and methods of the class, and the variables may be rewritten, There is no possibility of rewriting, each has an identification code,
The separation unit is
The identification code is discriminated, the class variable that may be rewritten is stored in the first nonvolatile memory, and the class variable that is not likely to be rewritten And a method of storing the class method in the second nonvolatile memory. In any one of claims 1 to 3,
An encryption processor for encrypting the remaining portion to be stored in the second nonvolatile memory;
The memory card, wherein the first nonvolatile memory, the separation unit, and the encryption processing unit are formed on the same chip. In any one of claims 1 to 3,
The first nonvolatile memory is an EEPROM;
The memory card, wherein the second nonvolatile memory is a flash memory.

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