JP2957724B2 - EEPROM card - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EEPROM card,
In particular, the present invention relates to a method for protecting a header area in which management information of a storage area is written.

[0002]

2. Description of the Related Art Conventionally, an electronic still camera uses an SRAM for a memory card. However, the SRAM requires a backup power supply circuit and has a disadvantage that the unit cost per bit is high. In recent years, EEPROM cards that do not require battery backup and that can be electrically erased in block units have been put into practical use.
With a capacity of 1 Mbit, it is suitable as a final storage medium for image data. EEPROM used in electronic still cameras
The storage area of the card stores one frame of image data in the form of a packet, and is provided with a packet header that stores information for managing a plurality of packets collectively. All packets belonging to multiple packet headers are managed in a memory allocation table (MAT).

A packet is composed of a cluster which is a minimum management unit of a memory. The packet header, a plurality of packets for the packet number of the packet head cluster number, the number of used clusters, residual number of clusters, and the packet management information, such as, such as pressurized data with that related to the image of the packet is written. The content of the packet header is rewritten every time the packet to which the packet belongs is written.

[0004]

The EEPROM has a characteristic that the rewriting limit is about 100 to 1000 times. The conventional packet header exceeds the rewrite limit faster than the packet when a plurality of image storage areas to which the image storage area belongs are used on average. There is a disadvantage that it cannot be rewritten.

An object of the present invention is to provide an EEPROM card which solves this drawback and has a small number of packet header rewrites and a long service life.

[0006]

According to the present invention, an EEPROM card on which information is written and read from an external device is provided.
An EEPROM having a plurality of unit areas and a plurality of headers in which management information relating to the plurality of unit areas is recorded, and in which the management information of the header is rewritten each time writing occurs in the unit area.
The storage area includes a plurality of unit areas,
A plurality of headers and a management number assigned to each of the plurality of headers are provided. When writing occurs in the unit area, the writing is performed by referring to the management information of the header having the maximum management number. Thus, the management information referred to is changed to be the management information of the header of the management number having the minimum value, and the minimum value is changed to a value obtained by adding 1 to the maximum value.

[0007]

The card according to the present invention includes a plurality of unit areas, a plurality of headers, and a management number assigned to each header in the storage area of the EEPROM. When the card is connected to an external device and receives a write command, the management number and the header are read out to the external device. The external device refers to the management information in the header of the management number having the maximum value, outputs the write address and information to the card, and performs the write. Thereafter, the external device changes the management information referred to by writing to the management information of the header of the minimum management number, and rewrites the card to change the minimum value to a value obtained by adding 1 to the maximum value.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments according to the present invention will be described in detail with reference to the accompanying drawings. The EEPROM card of this embodiment is used for an electronic still camera, and has an EEPROM memory cell 10 shown in FIG. In the memory cell 10, storage areas not directly related to the present invention are omitted. The storage area is a packet 20 containing image data for one frame.
And m headers 22 containing the management information are provided,
These areas are managed by the cluster 23 which is the minimum unit. The packet header 22 includes a packet number of each packet, a leading cluster number of the packet, the number of used clusters, and the like.
And packet management information such as the fine residual number of clusters, and the user information are written associated with the image recorded in the packet.

[0009] In the conventional method, since the packet header and the packet groups are supported fixedly, n-number of packets, change information such as Pakettohe header cluster As each one write is performed, Pakettohe Ddah m times,
Rewritten, hence the life of the EEPROM becomes 1 / m.
In the present invention, in order to avoid this, m packet headers 22 are provided for n packets 20, and each time a packet is written, a header management number 24 for replacing the packet header is included in each packet header. Provide.

In the initialization, the packet header 22 (1, 2,.
.. M) is set to 0. When a write request (WR1) is generated, the header corresponding to the maximum header management number 24 is read. Those in this case any as the largest management number because all management number 24 0, for example, select f header 1, it writes the image data to any packet 1, thereby is managed by the system side
The content of the header 1 is changed. And the system side
Write the updated header contents to header 1
And the maximum header management number 0 plus 1 plus 1,
The management number 0 in the header 1 is rewritten to the management number 1 .

When the next write request (WR2) is generated, the header 1 corresponding to the maximum header management number 1 at this time is read, and based on the contents of the header 1 , information is written to, for example, an empty packet 5 and the system is written. Tube at the side
The content of the managed header is updated. Next, the system side
The updated header content in the header with the minimum management number
Da, for example is written in the header 2, the value 2 <br/> largest management numbers 1 to 1 plus this time, Ru rewritten <br/> management number 0 of the header 2 in the management number 2. As a result,
The management number of DA2 is the maximum management number. In this manner, when the packet is written m times (WR1 to WRm), the m packet headers 22 are used once each by the header management number 24. Therefore, the number of times the packet header 22 is used is 1 / m of the conventional one, and the shortening of the life of the EEPROM can be prevented.

In the above example, m packets are used once each. However, even when the same packet is rewritten a plurality of times , every time the header of the minimum management number is rewritten ,
The value obtained by adding 1 to the maximum management number is
To use as the Da management number. Further, by setting the packet management number to a relative number or a cyclic number, 1 to m can be used as the management number even if n> m.

The EEPROM card 30 of the embodiment has the circuit shown in FIG. The memory cell 10, the address control unit 32, the header address management unit 34, and an external device (not shown) are connected to a data bus 36. The external device transmits data to be written to the memory cell 10 and an address on the bus 36 to a signal D0. Transmitted as ~ D7.

The command control unit 38 is provided by the system as shown in FIG.
Mode signals A0 and A1 as shown in
The (binary value) identifies whether the signals D0 to D7 are the upper, middle, and lower start addresses of the address or data. When the address, the command control unit 38 sends a start address from the signal line a to the address control unit 32, the department 32 and this is latches. Command control unit 38
When receiving the write signal WR and the read signal RD from the system, the BUSY outputs the BUSY signal for guaranteeing the write time of the memory cell 10 to the system. Command control unit 38
Outputs the trigger signal b to the header address management unit 34,
Header address management unit 34 outputs the number c of searching a header management number 24 to the address control unit 32.

The address control unit 32 latches the start address from the command control unit 38 in a register (not shown), and stores the address transmitted from the external device to the bus 36 or the number c from the header address management unit 34. an address obtained by adding the output to the memory cell 10, a header management number 24, to perform the access of the header 22 and packet 20.

Prior to writing the image data, the system has an RD signal for reading the header information and a mode signal.
A0 and A1 are output to the command control unit 38, and addresses D0 to D7 of the header 22 are output to the bus 36. Command control unit 38
Sends a BUSY signal to the system side, and outputs an initial address corresponding to the values of the mode signals A0 and A1 to the address control unit 32 from the control line a. The address control unit 32 latches this in a counter (not shown). The address D0 to D7 of the header 22 transmitted from the external device to the bus 36 is added to the counter, and the header 22 of the memory cell 10 is read to the bus 36.

The command control section 38 outputs a trigger signal b to the header address management section 34. Header address management unit
34 outputs the number c for accessing the header management numbers 1 to m of the header 22 to the address control unit 32. Address control unit
32 causes the bus 36 to read out m header management numbers from the memory cell 10 based on the address obtained by adding this to the address counter. The header address management unit 34 receives this, and stores the maximum value and the minimum value therein. The header address management unit 34 outputs the number C ′ corresponding to the maximum header management number to the address control unit 32 again, and the address control unit 32 outputs the header data D0 to D7 is read to the bus 36. That is, RD
The signal is executed. The header address management unit 34 sends an end signal d to the command control unit 38, and upon receiving this, the command control unit 38 releases the BUSY signal.

The system selects an empty packet from the data of the header having the maximum value of the read header management number, and
The mode signals A0 and A1 and the signals D0 to D7 are output to the EEPROM card 30.The mode signals A0 and A1 indicate whether the signals D0 to D7 to be transmitted to the bus 36 are addresses or data, and the image data is transmitted to an empty packet. Is written.

When the writing of the image data is completed, the contents of the read header data are updated. Then, a value obtained by adding 1 to the maximum value of the header management number is written as a new management number in the area of the minimum header management number,
The contents of the header are changed to the updated data. In this case, by recording the number of rewrites in the header,
If this exceeds the usage limit, the system can, for example, issue an alarm to stop writing to the card, thereby preventing a recording failure.

[0020]

According to the present invention, the number of times of rewriting of the header of the EEPROM card can be reduced to 1 / m of the conventional one to extend the service life and prevent the number of rewriting times from being exceeded.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing an embodiment of an EEPROM card according to the present invention.

FIG. 2 is an explanatory diagram of a memory cell in FIG. 1;

FIG. 3 is an explanatory diagram of a mode signal in FIG. 1;

[Explanation of symbols]

 10 Memory cell 12 EEPROM card 32 Address control unit 34 Header address management unit 38 Command control unit

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-165936 (JP, A) JP-A-1-277397 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G06F 12/16 310 G06F 12/02 G11C 16/02

Claims (1)

(57) [Claims] 1. An EEPROM card in which information is written and read from an external device, wherein a plurality of unit areas in which the information is recorded and management information relating to the plurality of unit areas are recorded, and writing occurs in the unit area. EEPROM including a plurality of packet headers rewritten each time and a management number of the plurality of packet headers
An address control means for designating write and read addresses in the storage area; a bus means for transferring write and read addresses and write information from an external device to the previous storage area and address control means; Command control means for receiving, from an external device, a mode signal for identifying an address and data on the bus means, a write / read command to the storage area, and outputting a busy signal to stop access to the external device during writing; A header address management means for outputting information for accessing the management number to the address control means, storing a maximum value and a minimum value of the management number to be read, and a packet header having the minimum management number And a header address management means for designating When a write command is received from an external device, the address control means causes the bus means to read each packet header and its management number from the storage area, and sends the maximum and minimum values of the management number to the header address management means. When storing, the output of the busy signal is stopped, the external device selects a unit area for writing based on the management information of the packet header indicating the maximum management number, and a write address and write information for the unit area. Is output, the write information is written in the unit area specified by the address control means in correspondence with the write address, and further, a value obtained by adding 1 to the management number of the maximum value is
Rewriting as a management number of a packet header corresponding to the minimum value specified by the header address management means,
An EEPROM card, wherein management information changed by writing the information is written in the packet header.