JP2001312426A - Control circuit and control method for memory element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control circuit and a control method which protect a memory element having been mounted on a substrate and reset the protection. SOLUTION: This control circuit 1 is inserted into a signal line 7C1 of the memory element 7 having been mounted on the substrate and has an input part for signals 5a (RD, RST) transmitted by the signal line 7C1, a high-voltage input part 1b, an input part 1c for control signals 5b (OVP, RVP) for applying a high voltage V12, switch parts 1e and if which select the high voltage V12 as the high-voltage signals OVP and RVP when the control signals 5b are active and signals transmitted by the signal line when inactive, and an output part 1d which outputs the signals selected by the switch parts 1e and if.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a memory element control circuit and a memory element control method.

[0002]

2. Description of the Related Art In recent years, a flash memory has attracted attention among memory devices. That is, since the stored contents can be electrically changed, a backup power supply is not required, and the device is resistant to impacts, it is often used as a nonvolatile memory element of all electric devices. In addition, flash memories are inexpensive due to the small number of transistors constituting memory cells, and can be easily miniaturized, so that they are mounted on substrates of various devices.

Some flash memories have a protection function of dividing a storage area into several sectors and prohibiting writing of the memory for each sector. By using this protection mechanism, 2. Description of the Related Art A program such as a basic program (IPL program or BIOS program) of a microcomputer and a storage area in which important data is written are protected. Note that the protection function of the storage area of the flash memory enables protection and temporary release of protection by inputting a control signal of a higher voltage than usual to a predetermined signal line among signal lines of the flash memory.

[0004] In addition, some memory devices such as EEP-ROMs can rewrite stored contents by inputting a high-voltage control signal to a predetermined signal line among the signal lines.

The writing of a program into these memory elements is performed, for example, by using an I / O that detachably supports the memory elements.
It has been performed using an electronic circuit such as a ROM writer that has a C socket and enables data to be written to a memory element. Then, for example, in the case of a flash memory, an area in which a program is written is protected, and the protected flash memory is mounted on a board on which a microcomputer of an electric device is mounted.

[0006]

However, in the case where the electric equipment on which the flash memory is mounted is manufactured in a variety of types and in small quantities, the flash memory once mounted on the substrate is protected. In some cases, it is necessary to change the program written in the area. For this reason, for example, when the specifications of the electric device equipped with the flash memory are changed, or when the program written in the flash memory needs to be upgraded due to some inconvenience, the flash memory is removed from the board. Therefore, it is necessary to rewrite the data with a ROM writer or the like again, or to replace it with another flash memory.

For this reason, it is inevitable that rewriting the protected data written in the mounted flash memory requires a great deal of trouble. Therefore, conventionally, when a program written in the flash memory is changed, the entire board is replaced.

A signal input to the signal line of the flash memory is normally a low voltage such as 3.3 V or 5 V even at a high level, and a digital circuit equipped with the flash memory has a power supply voltage of 3. A voltage of 3 V or 5 V is supplied. On the other hand, the control of protection or release of protection of the flash memory is performed in a state where a voltage (for example, 12 V) higher than the voltage level of the normal signal is supplied.

Therefore, the flash memory normally mounted on the board does not receive a signal of a voltage level higher than the power supply voltage, so that the protected data can be surely protected. In other words, there has been no circuit configuration that enables setting of protection or temporary release of protection of a flash memory on a board that performs a normal memory operation. The method of restricting the rewriting of the stored contents in such a memory element is not limited to the flash memory.
The same applies to a memory element such as an EP-ROM.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to control a memory element capable of setting protection and temporary release of protection for a memory element mounted on a substrate. An object of the present invention is to provide a method for controlling a circuit and a memory element.

[0011]

In order to achieve the above object, a control circuit for a memory element according to the present invention is a control circuit inserted into a signal line of a memory element mounted on a substrate, wherein An input part of a signal transmitted by the input part, a high voltage input part, an input part of a control signal for applying the high voltage, and selecting the high voltage as a high voltage signal when the control signal is in an active state. And a switch unit for selecting a signal transmitted by the signal line when the control signal is in an inactive state, and an output unit for outputting the signal selected by the switch unit.

Therefore, the control circuit for the memory element can directly write data to the memory element mounted on the substrate. Therefore, even if a program or important data to be stored in the memory element is changed, the memory element can be written. Need not be removed from the board. In other words, it is possible to minimize the time and effort required when a specification change is made to an electrical device using the memory element or a version is upgraded by maintenance or the like.

In particular, when the memory element is a flash memory, protection and temporary release of protection can be set for each sector obtained by dividing the storage contents in the same element.
A storage area in one element can be divided into a read-only area (functioning as a ROM) and a readable / writable area (functioning as a RAM). Depending on the software,
Software operation can be switched by software between the normal operation of the flash memory as a memory and the setting of protection or temporary release of protection. That is, the protection of the flash memory can be temporarily released or the protection can be set only by the operation on the software.

[0014] Then, a program or data can be written into the unprotected area by software. That is, when a problem such as an operation error occurs due to a program or data written in the flash memory, the trouble can be solved without changing the hardware.

Further, the allocation of the read-only area and the readable / writable area in one flash memory can be freely changed after mounting on the board, so that versatility can be provided. Then, the size of the substrate can be reduced, and the manufacturing cost can be reduced.

When it is not necessary to perform a rewriting operation on a protected memory element, for example, when rewriting a program or data using the control circuit of the memory element is completed and a normal memory operation is performed, By grounding the high voltage input unit, a voltage higher than the normal high level is not erroneously applied during the normal memory operation. That is, even if the switch unit is operated due to some unexpected event such as a runaway of the CPU, there is no fear that the protection of the memory element is unintentionally released.

According to the method of controlling a memory element of the present invention, a control circuit is inserted into a signal line of a memory element mounted on a substrate, and when a control signal input to the control circuit is in an inactive state, the signal line is used. By supplying a transmitted signal to the memory element and supplying a high-voltage control signal to the memory element when the control signal is in an active state, setting of protection and temporary release of protection for the memory element are performed. It is characterized by.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a control circuit 1 for a memory element according to the present invention will be described below with reference to FIG. In FIG.
Reference numeral 2 denotes a microcomputer (hereinafter, referred to as a microcomputer 2) on which the control circuit 1 for the memory element of the present invention is mounted. Reference numeral 3 denotes an electric device (hereinafter, referred to as an analyzer) having an analysis unit 3a as an example of a control target controlled by the microcomputer 2. 3),
Reference numeral 4 denotes an information processing device (hereinafter, referred to as a personal computer 4) which is connected to the analyzer 3 and which can be operated.

The analyzer 3 has a power supply circuit 3b for supplying at least a power of, for example, 5 V DC as a power supply voltage supplied to the microcomputer 2 and a higher power of 12 V DC. The power supply circuit 3b supplies power to the analysis unit 3a.

Reference numeral 5 denotes a microprocessor (hereinafter simply referred to as a CPU 5) which is a main arithmetic processing unit of the microcomputer 2, and 6
Reference numerals a and 6b denote interfaces, and reference numeral 7 denotes a flash memory which is an example of a memory element to be controlled by the control circuit 1. In this example, the description of other elements is omitted for simplicity of description,
The microcomputer 2 has a memory element such as a D-RAM or an S-RAM serving as a main memory in addition to the flash memory 7.

The flash memory 7 of this embodiment divides its storage area into several sectors 7a to 7z, and
Ｚ7z has a protection function (protection setting and protection release) for inhibiting writing to the memory, and has at least a data bus 7D and a control signal line 7C comprising an address bus and an input section for various control signals. are doing. The control signal line 7C of the present embodiment is divided into a signal line 7C ₁ which is used to set the protection of the flash memory 7, a signal line 7C ₂ unrelated to the setting of the protection.

[0022] The control circuit 1 is intended to be inserted between the signal line 7C _1, an input unit 1a of the signal 5a carried by the signal line 7C _1, the power of the DC 12V from the power supply circuit 3b ( hereinafter, a high voltage input section 1b for inputting a called high voltage V ₁₂₎ which in order to distinguish it from the power supply voltage 5V, C in order to apply the high voltage
An input unit 1c of the control signal 5b outputted from the PU5, outputs one of the signal 5a inputted to the high voltage V ₁₂ or the input unit 1a selected by the control signal 5b to the signal line 7C ₁ And an output unit 1d. Incidentally, 2s is a switch for outputting a high voltage V ₁₂ or 0V to the high voltage input unit 1b.

FIG. 1 discloses that the control signal 5b is directly output from the CPU 5 for the sake of simplicity, but the present invention does not limit the members that generate the control signal 5b. Absent. That is, although omitted in the above description, the control signal 5b is configured to be output from another logic circuit different from the CPU 5. Conversely, the control circuit 1, the CPU 5, the input / output interfaces 6a, 6
b, a one-chip microcomputer in which the flash memory 7 and the like are housed in one package may be formed.

FIG. 2 is a diagram showing an example of the control circuit 1. As shown in FIG. 2, the signal 5a carried by the signal line 7C ₁ is a example RD, a RST, control signal 5b for selecting a signal to be output to the signal line 7C ₁ is a OVP, a RVP. Also, 1e and 1f are controlled by the control signals OVP and RVP, respectively.
D, is selectively switched switch unit RST or high voltage V _12.

The switch sections 1e and 1f include, for example, rectifiers D ₁ and D ₂ inserted in the transmission direction of the signals RD and RST transmitted by the signal line L, and the rectifiers D and D2.
₁ , a pull-down resistor R ₁ connected downstream of D ₂ ,
R ₂ and switch elements T ₁ , T ₂ (for example, transistors) provided between the pull-down resistors R ₁ , R ₂ and the ground G and intermittently connected by input of control signals OVP, RVP. ing. Further, connecting the high voltage V ₁₂ via a pull-up resistor R _3, R ₄ between said pull-down resistor R _1, R ₂ and transistor T _1, T _2. Although B ₁ and B ₂ are buffers, they may be omitted.

By configuring the switch sections 1e and 1f as described above, the waveform propagation delay generated in the signals RD and RST in the normal state transmitted by the signal line L can be reduced by _one rectifying element D ₁ and D _2. And the operating speed during normal operation can be increased accordingly. That is, the insertion of the control circuit 1 does not hinder normal memory operation.

[0027] Further, according to the above configuration, the signal switching can be performed easily.
The number of parts can be reduced as much as possible. Soshi
Therefore, the transistor is controlled by the control signals OVP and RVP.
Star T ₁, T_TwoBy switching the
Resistance R₁, R_TwoCan be disconnected from the ground
As a result, the transistor T₁, T_TwoConnected to the collector side of
High voltage V₁₂Can be supplied to the signal line L.

The control circuit 1 having the above-described configuration uses the control signal OV
When P and RVP are driven to the high level, the signal levels of the signals RD and RST propagate to OE and RES of the output unit 1d as they are. On the other hand, the control signal OVP, Driving RVP low level, the transistor becomes OFF, the signal input to the input section 1a RD, OE regardless of the signal level of the RST, the high voltage V ₁₂ to the RES is applied.

That is, in this example, the control signals OVP, RV
P is a low-active control signal, the signal OE output from the output unit 1d is an RD having an output voltage of 5V or an OVP having an output voltage of 12V, and the signal RES is an RST having an output voltage of 5V.
Or, it becomes an RVP with an output voltage of 12V. It goes without saying that the present invention does not limit the control signal 5b input to the control circuit 1 to low active.

Therefore, the CPU 5 controls the control signals OVP,
By outputting a low level signal to the RVP, the flash memory 7 which has already been mounted on the substrate, it is possible to apply a control signal of the high voltage V ₁₂ at any, formed in the storage area of the flash memory 7 Sectors 7a-
7z can be protected or the protection can be temporarily released.

The configurations of the switches 1e and 1f are not limited to those described above, but may be formed using a semiconductor element such as an analog switch or a semiconductor relay. If the operation speed is sufficient, the switch units 1e and 1f may be relays.

In this embodiment, since the personal computer 4 is connected to the analyzer 3, setting of protection to the flash memory 7 and writing of programs and data can be performed through the personal computer 4. . That is, when the analyzer 3 is upgraded due to a function expansion or a specification change, or when maintenance is performed, the program written in the flash memory 7 can be executed without removing the flash memory 7 from the board constituting the microcomputer 2. The data can be arbitrarily rewritten by software from the personal computer 4 side.

Therefore, maintenance and expansion of the analyzer 3 can be performed very easily, and the time and labor required for the maintenance and extension can be reduced. In addition, it is possible to solve the problems caused by unnecessary remodeling of hardware and the cost of additional components.

[0034] If it is not necessary to apply a high voltage V _12, that is, if not performed at all settings for protection, said switch 2s at the input side of the high voltage V ₁₂
Should always be switched to the 0V side. Alternatively, the high-voltage input section 1b of the control circuit 1 may be subjected to a pull-down process. That is, by switching the switch 2s to the 0V side or performing a pull-down process, the CPU 5s
Even if the control signals OVP and RVP are unintentionally output due to runaway of the flash memory or the like, it is possible to prevent the flash memory 7 from being unprotected or unintentionally protected. .

Furthermore, after the switch 2s is multiplied by the protection against the switching to the power supply circuit side when to change the program or data to the flash memory 7, to allow supplying a high voltage V _12, a flash memory 7 Alternatively, the switch 2s may be used to switch it to the 0V side again. In this case, the switch 2
By s, switching can be performed so that programs and data can be rewritten by software only during maintenance.

In this embodiment, the flash memory 7 is used to protect a part of the storage area to make it a read-only area such as a ROM, and the other part to be a non-volatile RAM.
And the ratio between the read-only area and the readable / writable area can be changed after the board is mounted. That is, the versatility of the flash memory 7 can be increased.

Further, since the flash memory 7 can be formed to be small in size with respect to its capacity, not only can the microcontroller 2 be reduced in size, but also when the microcomputer 2 is formed as a one-chip microcomputer, the control circuit 1 can be used. By incorporating the same, the same effect can be obtained, and further downsizing can be achieved.

Although the above example discloses an example in which the flash memory 7 is mounted on the substrate of the microcomputer 2 formed in the analyzer 3, the present invention is limited to this point. is not. That is, the microcomputer 2 is not provided in the analyzer 3 but may be provided in all electric devices. For example, when the electric device 3 is a terminal adapter or a mobile phone, for example, the basic program written in the flash memory 7 can be rewritten later, so that new functions considered with the times can be added later. Can be added.

[0039]

As described above, according to the present invention, since data can be directly written into a memory element mounted on a substrate, even when a program or important data to be stored in the memory element is changed, the memory can be written. There is no need to remove the element from the substrate. That is, it is possible to minimize the time and effort required to change the specifications of the electrical device using the memory element or to upgrade the version by maintenance or the like.

When a program or data written in the flash memory causes a trouble such that an operation error occurs, even if the area where the program is written is protected, this program is temporarily stored. Program can be changed by software. That is, the trouble can be solved without changing the hardware. As for the circuit configuration, by minimizing the required number of components, the substrate can be reduced, and the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment using a control circuit of a memory element which is an example of the present invention.

FIG. 2 is a diagram illustrating a configuration of the control circuit.

[Explanation of symbols]

Reference numeral 1: memory element control circuit, 1 a, 1 c ... input unit, 1 b
... High-voltage input section, 1d ... output section, 1e, 1f ... switch section, 5a (RD, RST) ... signal, 5b (OVP, RV)
P): control signal, 7: memory element, 7C ₁ : signal line, V ₁₂ : high voltage.

Claims (2)

[Claims] 1. A control circuit inserted into a signal line of a memory element mounted on a substrate, the control circuit being adapted to apply an input part for a signal transmitted by the signal line, a high voltage input part, and the high voltage. A control signal input unit, and a switch unit that selects the high voltage as a high voltage signal when the control signal is in an active state, and selects a signal transmitted by a signal line when the control signal is in an inactive state. And an output unit for outputting a signal selected by the switch unit. 2. A control circuit is inserted into a signal line of a memory element mounted on a substrate, and a signal transmitted by the signal line is supplied to the memory element when a control signal input to the control circuit is in an inactive state. Supplying a high-voltage control signal to the memory element when the control signal is in an active state, thereby setting protection and canceling protection of the memory element. .