JPH07334992A - Non-volatile memory - Google Patents

Abstract

PURPOSE:To perform the programing without useless erasing process of data by storing an erasing flag indicating whether data in a data recording region has been erased or not, in an erasing flag region. CONSTITUTION:A memory cell array has a memory block 2, a data region 3 and a flag registration region 4. An address control circuit 12 specifies an address of the memory block 2 based on an address signal AS. A command control circuit 13 receives a control signal CS, instructs a region 3 of the array 1 to perform programing and reading out data DS or erasing a block, while instructing a region 4 to perform setting or resetting an erasing flag. An erasing state discriminating circuit 14 reads out an erasing flag from the region 4, and discriminates a set state. The circuit 13 performs block erasing, programing, and set/reset of a flag in accordance with the discriminated result of the circuit 14. Therefore, useless erasing of a block can be omitted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-volatile memory, and more particularly to a data rewritable non-volatile memory.

[0002]

2. Description of the Related Art A nonvolatile semiconductor memory device (hereinafter referred to as a semiconductor device) can store data. To store data in a semiconductor device,
It is necessary to program the desired data using a programming device.

A semiconductor device of a flash memory has a plurality of memory blocks. One memory block has a plurality of memory cells for storing data,
For example, it consists of 512 bytes. A semiconductor device is programmed by using a memory block as a minimum unit.

FIG. 2 is a flow chart showing a conventional method for programming a semiconductor device. After connecting the programming device to the semiconductor device, the semiconductor device is programmed by performing the following processing.

First, in step P1, a program command is input to the programming device. The program command is a command for instructing a program to the semiconductor device, and includes information of an address and data to be programmed.

At step P2, the address designated by the program command is set. Since the program is executed in memory block units, the address setting here sets the address of the memory block and specifies the memory block.

At step P3, the data in the specified memory block is erased. By erasing the data, the memory cell is set to the high state (“H”), and the entire memory block is filled with the erase data. The erased data is, for example, 8-bit data of "H".

The memory cell is, for example, in a high state ("H") by erasing data, and then is in a low state ("L") by performing writing and electron injection. Since programming from "L" to "H" is not possible, the pre-erase processing performed in step P3 is required before programming.

At step P4, the program data designated by the program command is transferred to the specified memory block. 512 memory blocks
If it is a byte, 512 bytes of data are transferred.

In step P5, the transferred data is programmed in a predetermined memory block, and the programming process for the semiconductor device is completed. As mentioned above,
When a program command is input, the block must be erased (step P3) before programming (step P5).
I do. What accepts such a command format is hereinafter referred to as an overwrite type.

On the other hand, when a program command is input,
A non-overwrite type accepts a command format for executing only a program without erasing blocks.
The non-overwrite type has an erase command independently of the program command, and the erase command is input before the program command is input. However, the erase command does not necessarily have to be input immediately before the program command.

[0012]

In the case of the overwrite type, when a program command is input, the data is always erased before programming regardless of the intention to erase the data or not. . However, when the memory block is already in the erased state, it is not necessary to erase the data again, and only the programming needs to be performed.

In the case of the non-overwrite type, since the erase command can be continuously input twice or more, forgetting that the erase command has already been input and input the erase command again. Sometimes it ends up. However, such an erase command is useless.

An object of the present invention is to provide a non-volatile memory for programming without performing unnecessary data erasing processing.

[0015]

The nonvolatile memory of the present invention has an erasure that stores an erasure flag indicating whether or not the data storage area corresponding to each data storage area having a plurality of memory cells has been erased. It has a plurality of memory blocks including a flag area.

[0016]

By storing the erase flag indicating whether or not the data storage area is erased in the erase flag area, it is possible to know whether or not the data storage area of the desired memory block is erased. If the data storage area is not erased, it is necessary to perform the program after the data is erased. If the data storage area is erased, the program can be performed without performing the data erase.

[0017]

1 is a memory cell array included in a semiconductor device according to an embodiment of the present invention. The semiconductor device is, for example, a flash memory (nonvolatile memory) having a memory cell array including a plurality of memory cells.
The memory cell array 1 is composed of a plurality of memory cells arranged two-dimensionally in the row direction and the column direction. A plurality of memory blocks 2 are arranged in the row direction, and one memory block is selected by the row address.

Each of the plurality of memory blocks 2 has a data area 3 and an erase flag registration area 4. The data area 3 is an area for storing data to be programmed,
For example, it is an area of 512 bytes. The erasure flag registration area 4 is an area in which a flag indicating whether or not the corresponding data area 3 is in a data erased state is stored, and requires at least a 1-bit area. If the erase flag is set, it indicates that the data area 3 has been erased and is in the erased state, and if the erase flag is reset,
It means that the program is performed after the data is erased.

At the time of manufacturing a semiconductor device, the memory cell array is initialized. All memory blocks 2
The data area 3 is erased and the erased data is stored. By erasing the data, the memory cell is in a state ("H") where electrons are not captured.

The erase flags in the erase flag registration areas 4 of all the memory blocks 2 are set. Considering the characteristics of the memory cell, the set state of the erase flag is preferably "L", which is the same as the data erase state, and the reverse state of the erase flag is preferably "H". The reason will be described later.

FIG. 3 is a flow chart showing a method for programming a semiconductor device of this embodiment. After connecting the programming device to the semiconductor device, the program is performed by performing the following processing.

In step Q1, a program command is input to the program device to instruct an address indicating a desired memory block and program data. In step Q2, the address designated by the program command is set and the memory block is specified.

At step Q3, the erase flag is read from the erase data storage area of the specified memory block.
In step Q4, it is checked whether the read erase flag is in the set state or the reset state. If the erase flag is set, it means that the data has already been erased.
No block erase is performed. In the initial state, all data areas are block-erased and the erase flag is set, so that data erase is not performed in the first programming.

When the erase flag is reset,
Since the previous data remains in the block, step Q5
To erase the block. Thereafter, in step Q6, the program data instructed by the program command is transferred to the specified memory block. In step Q7, the data transferred to the data area of the memory block is programmed.

At step Q8, since the data is programmed in the data area with the completion of the program, the erase flag is reset. By resetting the erase flag, the programming process for the semiconductor device is completed.

If the above program commands are used, the data area is always erased in the initial state. Therefore, the first program command for each memory block skips block erase (step Q5). To do. Therefore, the time required for the block erasing process becomes 0, and the total time required for inputting the program command is shortened.

When the memory block is programmed once, the erase flag is reset and remains in the reset state thereafter. Therefore, the processing time cannot be shortened for the second and subsequent program commands. However, this is sufficient if the semiconductor device is used for a purpose in which each memory block is programmed only once and is not rewritten thereafter.

Next, the erase command used for making it possible to shorten the time even for the second and subsequent program commands will be described. FIG. 4 is a flowchart showing a process by inputting an erase command for erasing the data area of the memory block.

In step R1, an erase command is input to the programming device to instruct to erase the data area of a desired memory block. In step R2, the memory block address designated by the program command is set, and the memory block is specified.

In step R3, the erase flag is read from the erase data storage area of the specified memory block.
In step R4, it is checked whether the read erase flag is in the set state or the reset state. If the erase flag is in the reset state, it indicates that the data area has not been erased. Therefore, block erase is performed in step R5, and the erase flag is set in step R6. On the other hand, if the erase flag is in the set state, it indicates that the data area has been erased, and therefore the processes of block erase (step R5) and erase flag set (step R6) are skipped. With the above, the process by inputting the erase command is completed.

For example, the erase command is effective when the image data continuously photographed by an electronic camera or the like is stored in the semiconductor device. The electronic camera can capture a single still image by pressing the shutter switch and capture the next image when the image data is completely programmed in the semiconductor device. Therefore, if the program time is shortened, it is possible to increase the number of frames per unit time that can be continuously shot by the electronic camera.

For example, when the electronic camera is not programming the image data in the semiconductor device, or in the background when other processing is being performed,
An erase command is executed in advance for a memory block in which image data is to be programmed. By doing so, when it is attempted to continuously program image data into a plurality of memory blocks by continuous shooting, only the program is executed without erasing the blocks, so the program time is shortened and the program time is reduced within a predetermined time. The number of frames that can be taken can be increased.

The program command shown in FIG. 3 described above is an overwrite type. However, the conventional overwrite type does not normally have a command for only block erasing as shown in FIG. Therefore, an example of a command capable of independently performing both the program and the block erase processing using one program command will be described below.

FIG. 5 is a flow chart showing a program process and a block erase process for a semiconductor device according to another embodiment. By using the program command, either the program process or the block erase process can be performed.

When performing the program processing, program data such as image data to be programmed is input together with the program command, and when erasing the block,
For example, 512 bytes of erase data for one block (for example, all "H") is input together with a program command.

First, a processing procedure when the program processing is performed first will be described. In step S1, a program command is input to the program device to instruct data such as image data to be programmed and an address. In step S2, an address is set and a memory block is specified.

In step S3, the erase flag is read from the specified memory block, and in step S4 it is checked whether the erase flag is set or reset. If the erase flag is in the reset state, the data is not erased yet, so the block is erased in step S5. If the erase flag is in the set state, the data is already erased and the block is not erased.

Then, in step S6, it is checked whether or not all the data input together with the program command are erase data (for example, all "H"). If the data to be transferred is general image data, etc., it is usually not all erased data, so the process proceeds to step S7.
Data such as image data is transferred to a predetermined memory block, and the transferred data is programmed in the data area in step S8. Then, the erase flag is reset in step S9. With that, the process ends.

Next, the processing procedure when the block erasing process is performed by the program command will be described with reference to the same figure. In step S1, a program command is input and, for example, erase data (for example, 512 bytes) for one block of all “H” and an address at which block erase is desired are designated. In step S2, an address is set and a memory block to be erased is specified.

In step S3, the erase flag is read from the specified memory block and it is checked in step S4 whether the erase flag is set or reset. If the erase flag is in the reset state, the data is not erased yet, so the block is erased in step S5. If the erase flag is in the set state, the data is already erased and the block is not erased.

After that, in step S6, it is determined that all the data input together with the program command are erase data, so the process proceeds to step S10 and the erase flag is set without executing the program (step S8).
With that, the process ends.

Although the case of the overwrite type has been described above, the case of the non-overwrite type will be described next. The non-overwrite type does not include block erase processing in the program command. To erase blocks,
Use the erase command.

FIG. 6 is a flowchart showing the processing of a program command for a non-overwrite type semiconductor device. In step T1, a program command is input to instruct an address and data for programming. In step T2, the address is set and the memory block is specified. In step T3, the data is transferred to the specified memory block. In step T4,
Program the transferred data in the data area. In step T5, the erase flag is reset and information indicating that the program has been completed is recorded. Then, the process ends.

The processing of the erase command used in combination with the above program command is the same as the processing of the erase command shown in FIG. When the program command is input, the erase flag is reset (step T5) after the program (step T4) is performed. After that, when an erase command is input, the block is erased because the erase flag is in the reset state. However, even if the erase command is continuously input after the erase command is input, the block erase is not performed because the erase flag is already set.

FIG. 7 is a block diagram showing the structure of a semiconductor device that performs programming or block erasing by the above-mentioned commands. Program commands and erase commands are input to the program device connected to the semiconductor device 10. Input / output interface (I / O) 11 of the semiconductor device 10 is supplied with necessary information according to a command from the programming device. I / O10 is
Address signal AS, data signal DS and control signal CS
Is output. The address signal AS and the data signal DS are an address and data for program or block erase, respectively, and the control signal CS is a power supply, a chip enable signal, and other necessary control signals.

The memory cell array 1 has a data area 3 and a flag registration area 4 as shown in FIG. The address control circuit 12 converts the address into a row address and a column address for designating an address in the memory block based on the address signal AS. In the memory cell array 1, the memory block is specified by the row address, and the address in the data area 3 or the erase flag registration area 4 of the specified memory block is specified by the column address. Then, the data DS is programmed or read with respect to the specified address.

The command control circuit 13 receives the control signal CS and stores the data D in the data area 3 of the memory cell array 1.
Instruct to program, read or block erase of S. Further, the erase flag registration area 4 is instructed to set or reset the erase flag.

The erasing state judging circuit 14 reads the erasing flag from the erasing flag registration area 4 and judges whether it is in the set state ("L") or the reset state ("H"). The command control circuit 13 performs block erase, program, and flag setting / resetting in accordance with the determination result of the erase state determination circuit 14.

As described above, in each block memory 2 of the memory cell array 1, the data area 3 and the erase flag registration area 4 are provided.
By providing, it is possible to have an erase flag indicating whether or not the data area 3 is in the erased state. By using the information of the erasing flag, it is possible to omit a wasteful block erasing process such as erasing the block of the data area 3 twice in succession, and to shorten the processing time.

Further, if the block is erased in advance by the block erase command when the program processing is not being performed, the program processing only needs to be performed when the electronic camera continuously shoots. The time required for processing can be shortened. In this case, the block processing steps are moved to a vacant time, and the overall time does not change, but the specific processing can be shortened, so that the effect is great.

At the beginning, it was stated that the data area 3 in the initial state at the time of manufacturing the semiconductor device is filled with the erase data and the erase flag is set. At this time, if the erase data is all "H" data, it is desirable that the set state of the erase flag is "L" and the reset state of the erase flag is "H". The reason will be explained.

When data is erased, the electrons trapped in the memory cell are released and become "H". Then, when the characteristics of the memory cell deteriorate, the injected electrons are spontaneously emitted, so that it easily changes from “L” to “H”. In exchange, it is hard to change from "H" to "L".

Therefore, the set state of the erase flag is set to "L".
By doing so, even if it naturally changes to “H”,
It is judged that the block has not been erased yet, and the block is erased again.

On the other hand, if the set state of the erase flag is set to "H" and the reset state is set to "L", the reset state ("L") changes to the set state ("H").
It becomes easy to change naturally. After the data area 3 is programmed and the erase flag is reset (“L”),
If it naturally changes to the set state (“H”), it is mistakenly determined that it is already in the erased state, and the block is not erased from the programmed state and the program is performed again. Become.

When the data area 3 which is not in the erased state is programmed, the programmed data is not reliable and the stored data value cannot be guaranteed. Such errors are fatal and should not be encountered. Therefore, the erase flag is set to "L".
Therefore, it is desirable that the reset state is "H".

The present invention has been described above with reference to the embodiments.
The present invention is not limited to these. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0057]

As described above, according to the present invention,
By checking the erase flag stored in the erase flag area, it is possible to know whether or not the data storage area of the desired memory block has been erased. Therefore, for example, the same data area is erased twice consecutively. It is possible to eliminate useless processing that is performed.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a memory cell array included in a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a program command for a semiconductor device according to a conventional technique.

FIG. 3 is a flowchart showing a program command for the semiconductor device of this embodiment.

FIG. 4 is a flowchart showing an erase command to a semiconductor device of this embodiment.

FIG. 5 is a flowchart showing a program command for a semiconductor device according to another embodiment.

FIG. 6 is a flowchart showing a program command for a non-overwrite type semiconductor device.

FIG. 7 is a block diagram showing a configuration of a semiconductor device according to this example.

[Explanation of symbols]

 1 Memory Cell Array 2 Memory Block 3 Data Area 4 Erase Flag Registration Area 10 Semiconductor Device 11 Input / Output Interface 12 Address Control Circuit 13 Command Control Circuit 14 Erase State Judgment Circuit

Claims (4)

[Claims] 1. A plurality of data storage areas (3) each having a plurality of memory cells, and a plurality of erase flag areas (4) each storing an erase flag indicating whether or not the corresponding data storage area has been erased. A non-volatile memory having a memory block (2). 2. The use of a non-volatile memory having a data storage area for storing data and an erase flag area for storing an erase flag indicating whether or not the data storage area has been erased. To erase the data and indicate that the data storage area has been erased,
And a step of setting an erase flag stored in an erase flag area to a set state. 3. The use of a non-volatile memory having a data storage area for storing data and an erase flag area for storing an erase flag indicating whether or not the data storage area has been erased. A method for programming a non-volatile memory, comprising: programming data; and resetting an erase flag stored in an erase flag area to indicate that the data storage area is not erased. 4. Use of a non-volatile memory having a data storage area for storing data and an erase flag area for storing an erase flag indicating whether or not the data storage area has been erased. The step of reading the erase flag, the step of checking whether the read erase flag is in the set state or the reset state, and erasing the data area assuming that the data area has not been erased only when the erase flag is in the reset state And a method of erasing data in a non-volatile memory, including