JPH1011277A - Computer device with electrically rewritable nonvolatile memory and nonvolatile semiconductor memory - Google Patents

Abstract

PROBLEM TO BE SOLVED: To store a program for changing stored contents to be executed in a computer device without increasing the number of the points of parts at the time of rewriting an operation program stored in an electrically rewritable nonvolatile memory. SOLUTION: At the time of changing stored contents in flash ROM 3, an IPL program stored in the flash ROM 3 is transferred to RAM 4. After transferring the IPL program to RAM 4, a switch control circuit 5 switches the mapping of a memory to execute the IPL program stored in RAM 4. The stored contents in flash ROM 3 is erased by the IPL program to write an updated program supplied through an RS-232C interface 12 in flash ROM 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a computer device having an electrically rewritable nonvolatile memory into which an operation program is written, and a nonvolatile semiconductor memory suitably used for the computer device.

[0002]

2. Description of the Related Art In a computer, a program for rewriting an application program written in an electrically rewritable nonvolatile semiconductor memory or a flash EPROM which is a kind of rewritable nonvolatile semiconductor memory is an IPL. It is called a program and is stored in a dedicated ROM.

[0003] As an example of the above-described apparatus, Japanese Patent Application Laid-Open No.
Japanese Patent Application Publication No. 139064 discloses an electronic apparatus. In an electronic device, a control program for controlling the operation of the device is stored in a flash ROM, which is an electrically rewritable nonvolatile memory, and an IPL program is stored in the ROM. The IPL program includes a flash ROM rewriting program together with a system start-up program that operates when the power is turned on.

When a bug is found in the control program stored in the flash ROM, the SRAM memory card storing the debugged control program is rewritten in order to rewrite the control program. Connected to. When the SRAM memory card is connected, the ROM system start-up program
It is determined that the SRAM memory card has the control program, and the debugged control program is read and stored in the internal RAM based on the flash ROM rewriting program. When power for rewriting data is supplied to the flash ROM, the control program stored in the flash ROM is erased, and the debugged control program stored in the internal RAM is replaced with the flash ROM.
Is written to.

There has also been proposed an apparatus for storing an IPL program in a rewritable nonvolatile semiconductor memory or flash EPROM without providing a dedicated ROM for storing the IPL program. The IPL program includes a rewrite program for changing an application program. The rewrite program can be transferred to the RAM and operated to change the storage content of the ROM.

In an apparatus in which an application program and an IPL program are stored in an electrically rewritable memory such as a flash EPROM or a rewritable nonvolatile semiconductor memory, writing to the flash EPROM is performed due to external factors such as static electricity and noise. The stored contents may be rewritten. If the application program becomes abnormal, the IPL program can be operated to write the application program into the ROM again, but if the IPL program becomes abnormal, the normal program must be written to the device. Is no longer possible.

[0007] For example, in a computer device disclosed in Japanese Patent Application Laid-Open No. 5-342094, a technique for solving such inconvenience is used. Computer equipment
The system comprises an electrically rewritable ROM storing an application program and an IPL program, and a suppressing means for suppressing output of a chip select signal for selecting the ROM when the device is reset.

In the computer, when the IPL program becomes abnormal, a memory card storing a normal IPL program is connected to the device. When the device is reset after the connection of the memory card, the memory card is selected by the output from the inhibiting means, and the normal storage content changing program is executed from the IPL program stored in the memory card. An application program and an IPL by a storage content changing program
The program is written into the ROM of the computer device.

[0009]

In the electronic device, a dedicated ROM for storing a storage content change program is provided, which causes a problem that the number of components of the device increases and the component cost increases.

In the computer device, when an IPL program stored therein becomes abnormal, the IPL
Since the memory card storing the program is connected, the IPL program is read from the memory card, and the application program and the IPL program are written in the ROM, an interface dedicated to the memory card and a connector for connecting the memory card are provided inside the apparatus. It is necessary to provide such a device, which results in an increase in the size of the substrate of the device and an increase in cost due to the provision of the connector and the like.

Although there is a method of connecting a memory board storing a storage content change program to a device and rewriting the storage content change program, a space for mounting the board and a connector for connecting the board are also required. Become.

An object of the present invention is to provide a computer device which operates in accordance with an operation program stored in an electrically rewritable non-volatile memory, and which has a simple and highly reliable method for changing storage contents for rewriting an operation program. An object of the present invention is to provide a computer device including an electrically rewritable nonvolatile memory capable of executing a program.

[0013]

According to the present invention, there is provided an electrically rewritable nonvolatile memory in which a program for operating a computer including a program for changing storage contents is written, and a method for writing and reading storage contents. Possible RAM,
The program for changing the storage contents from the non-volatile memory
M; a program transfer unit for transferring the data to M;
Control for responding to a storage content change instruction from the change instruction means and electrically rewriting the storage content of the nonvolatile memory in accordance with the storage content change program transferred from the nonvolatile memory to the RAM by the program transfer means. And a computer device comprising an electrically rewritable non-volatile memory. According to the present invention, an operation program for operating the computer device is written in the electrically rewritable nonvolatile memory of the computer device. When changing the contents stored in the non-volatile memory, the change instructing means instructs the start of the operation of changing the stored contents. The program transfer means reads the storage content change program from the operation program stored in the non-volatile memory, and
Write to AM. The control means executes the storage content changing program transferred to the RAM, and electrically rewrites the storage content of the nonvolatile memory. Therefore, the program executed when changing the storage content of the electrically rewritable nonvolatile memory is transferred from the nonvolatile memory to the RAM when the operation program is rewritten, and is executed. The operation program can be rewritten without providing a dedicated ROM or the like for storing the change program in the computer device.

Further, the present invention is characterized in that it has a protection means for performing write protection on the program for changing the stored contents transferred to the RAM by the program transfer means. According to the present invention, the storage content changing program transferred to the RAM is protected by the protection means, and is not written. Therefore, in order to rewrite the storage content of the nonvolatile memory, when the storage content change program stored in the RAM is being executed, the storage content change program stored in the RAM is rewritten due to noise or the like. Although the program may run out of control, the rewriting of the program is prevented by the protection means, so that the storage content changing program can be operated stably.

The control means of the present invention operates according to a program written in a predetermined storage area of the nonvolatile memory when the change instruction is not instructed by the change instructing means, and the change operation is performed by the change instructing means. When instructed, there is provided a program processing means which operates in accordance with a program stored in a storage area of the RAM to which a program for changing storage contents is transferred by the program transfer means. According to the present invention, the program processing means of the control means, when the change operation is not instructed by the change instructing means, according to the program written in the predetermined storage area of the electrically rewritable nonvolatile memory. Operate. When a change operation is instructed by the change instructing means, the operation is performed in accordance with the stored contents of the RAM to which the program for changing the stored contents is transferred by the program transferring means. Therefore, depending on whether or not a change operation is instructed by the change instructing means, a program written in a predetermined storage area of the nonvolatile memory or a program for changing storage contents stored in the RAM is selected. Therefore, according to a desired operation, the nonvolatile memory or RA
A program stored in a predetermined area of M can be read and executed.

The nonvolatile memory according to the present invention is a flash EPROM. According to the present invention, the electrically rewritable non-volatile memory in the computer device is constituted by a flash EPROM. Therefore, when the entire memory area or the memory area is rewritten in blocks each having a predetermined size. Even if there is, rewriting can be performed reliably.

The nonvolatile memory according to the present invention includes a register in which a protection code is stored at the time of manufacture, input means for inputting data when the storage content is changed, and data input to the input means and stored in the register. And a comparison protection means for permitting a change in the stored content only when the protection codes are matched with each other. According to the present invention, when changing the storage content of the electrically rewritable nonvolatile memory, it is determined whether the data input from the input unit matches the protection code stored in the register. The determination is made by the comparison protection means, and writing is permitted only when they match, and the stored contents are rewritten. Therefore, the storage contents of the nonvolatile memory can be changed only when the same data as the protection code can be input from the input means, thereby preventing the storage contents of the nonvolatile memory from being rewritten carelessly. can do.

The present invention relates to an electrically rewritable nonvolatile semiconductor memory, a register in which a protection code is stored at the time of manufacture, input means for inputting data when storage contents are changed, and data input to the input means. And a protection code that compares the protection code stored in the register and allows the storage contents to be changed only when they match. According to the present invention, when changing the storage content of the electrically rewritable nonvolatile semiconductor memory, it is determined whether the data input from the input unit matches the protection code stored in the register. Is determined by the comparison protection means, writing is permitted only when they match, and the stored contents are rewritten. Therefore, the storage content of the nonvolatile semiconductor memory can be changed only when the same data as the protection code can be input from the input means, and the storage content of the nonvolatile semiconductor memory can be rewritten carelessly. Can be prevented.

[0019]

FIG. 1 is a block diagram showing a configuration of a remote printer 1 according to a first embodiment of the present invention. The remote printer 1 is a CPU (Central Processing Unit)
2, a flash ROM 3, a RAM 4, a switching control circuit 5, a switching switch 6, an input key group 7, a display panel 8, a buzzer 9, a DIP switch 10, a printer 11, and an RS-232C interface. 12 are included.

The remote printer 1 is a printer used as an external connection printer of an information processing apparatus such as an electronic cash register, and an external connection interface RS
Processing such as printing is performed based on the command and data received via the 232-C interface 12. By switching the setting of a DIP switch 10 described later, it is possible to set the communication speed and communication data format according to the type of the information processing apparatus.

The CPU 2 includes a flash ROM 3 and a RAM
4, control of input / output of signals in the input key group 7, the display panel 8, the buzzer 9, the printer 11, the RS-232C interface 12, and the like. Also, RS-
Data supplied from an external computer device or the like is processed through the 232C interface 12 and supplied to the printer 11 as print data.

The flash ROM 3 is a kind of electrically rewritable nonvolatile semiconductor memory. The flash ROM 3 can be rewritten in units of blocks obtained by dividing a storage area into a predetermined size, and does not require backup of the memory when the power is turned off. It is. The flash ROM 3 stores an IPL program including an after-mentioned storage content changing program and an operation program. The IPL program includes an initialization program for initializing a work area in the RAM 4, and the like.
It is configured to include a storage content changing program executed when the storage content of the flash ROM 3 is rewritten. The ON / OFF state of the changeover switch 6 is manually switched by, for example, an operator who attempts to rewrite the operation program, and the output O is switched according to the ON / OFF state.
The signal level of the UT is determined.

The input key group 7 is provided with a plurality of keys for setting the status of the remote printer 1, and includes, for example, a journal key 16, a receipt key 17, and an online key 18. Journal key 1
Reference numeral 6 designates a journal-side paper feed in the printer 11, and a receipt key 17 instructs a receipt-side paper feed in the printer 11. Online key 18 is RS-2
The signal is turned on when receiving data from an external computer via the 32C interface 12, and is turned off when communication is not performed.
F.

The display panel 8 is a panel for displaying the status of the remote printer 1, and includes, for example, a plurality of LEs.
D (light emitting diode). The display panel 8 has a power lamp that is turned on when the power is turned on and is turned off when the power is off, an online lamp that is turned on when the communication line is connected and turned off when the communication line is not connected, and turned on when an error occurs when the flash ROM 3 is rewritten. And an error lamp. The buzzer 9 is a device for notifying the status of the remote printer 1 by sound. For example, at the time of rewriting the flash ROM 3, the buzzer sounds once when the rewriting is completed normally, and when the abnormality occurs, the intermittent buzzer sounds. To notify that an error has occurred.

The DIP switch 10 is composed of a plurality of state setting switches.
Make settings such as communication data format. The printer 11
Printing is performed based on printing data supplied from the CPU 2. Further, at the time of testing the remote printer 1 and at the time of confirming the settings, predetermined printing read from the flash ROM 3 or the like is performed.

FIG. 2 is a block diagram showing the configuration of the switching control circuit 5, and FIG. 3 is a diagram for explaining switching control by the switching control circuit 5. The switching control circuit 5 includes a decoding circuit 21, a mapping switching circuit 22, and a write protection circuit 23.

Decoding circuit 21 decodes signals AREA 1 and AREA 1 based on an address signal given from CPU 2.
AREA2 is output to the mapping switching circuit 22. The mapping switching circuit 22 outputs the decode signals AREA1, AR
Based on EA2 and the output OUT of the changeover switch 6,
Flash ROM 3 and RAM 4 after CPU 2 reset
And outputs a signal indicating which of the above is referred to by the CPU 2. The flash ROM 3 receives a chip select signal SELO for the flash ROM, and the RAM 4
A chip select signal SELA for M is applied.

Chip select signals SELO, SELA
, Only one of them is at the high level. In the flash ROM 3 and the RAM 4, for example, the level of the applied signal is set to the area AR1 when the level is high, and is set to the area AR2 when the level is low.

The mapping switching circuit 22 has an address decode signal AREA1,
For AREA2, check if switch 6 is ON
Flash ROM 3 and RA
The chip select signals SELO and SELA are output to M4. When the changeover switch 6 is OFF, FIG.
As shown in (1), flash RO is set as area AR1.
M3 is allocated, and RAM4 is allocated as area AR2. When the changeover switch 6 is ON, the RAM 4 is allocated to the area AR1 and the flash ROM 3 is allocated to the area AR2 as shown in FIG. The CPU 2 executes the program with reference to the head address of the memory allocated to the area AR1.

The write protection circuit 23 receives the write signal WR from the CPU 2 and the output OUT of the changeover switch 6. When the write signal WR supplied from the CPU 2 becomes high level and writing to the RAM 4 is requested, whether or not to permit writing to the RAM 4 is determined depending on which signal level of the output OUT is. The signal level of the write signal RWR is determined.

When it is determined from the output OUT of the changeover switch 6 that the changeover switch 6 is OFF, R
Writing is not permitted in the area where the AM4 IPL program is copied. When it is determined from the output OUT of the changeover switch 6 that the changeover switch 6 is ON, the writing to the RAM 4 is permitted when the write signal WR becomes high level.

FIG. 4 shows an arrangement of programs stored in the flash ROM 3 and the RAM 4 in the remote printer 1. FIG. 4A shows the flash ROM 3 and the RAM 4 before executing a program for changing storage contents in the IPL program. Flash ROM3
The IPL program is stored in the area R1 from the first address of the above, and the operation program is stored in the area R2. The region R3 of the RAM 4 is a work area. In the work area of the RAM 4, for example, a key buffer for storing key data indicating a key input using the input key group 7 is set.

As shown in FIG. 3A, the flash RO
If M3 is selected as the area AR1, immediately after the reset, the I stored in the area R1 of the flash ROM 3
The PL program is read and executed. The operation program stored in region R2 is read and executed by the IPL program.

FIG. 4B shows the flash ROM 3 and the RAM 4 when the program for changing the stored contents is executed.
And When the memory change program is executed,
IPL stored in area R1 of flash ROM3
The program is read and stored in the area R4 starting from the first address of the RAM4. An area R5 following the area R4 is a work area.

After the IPL program is stored in the area R4 of the RAM 4, the changeover switch 6 is changed over to the state shown in FIG.
Each area AR1, AR2 is defined as shown in (2). When the areas AR1 and AR2 are determined and then reset, for example, the IPL program of the area R4 is executed.

When the IPL program is being executed,
When the execution of the program for changing the storage content is instructed, the IPL program and the operation program stored in the flash ROM 3 are erased. The storage contents changing program is a program that, after erasing each program in the flash ROM 3, updates the updated IPL program and the operation program supplied through the RS-232C interface 12 in the work area of the region R5 in the RAM 4. Store in the data reception buffer. The updated IPL program and operation program are read from the program data reception buffer by the storage content changing program, and are stored in the areas R6 and R7 of the flash ROM 3 as shown in FIG.

FIG. 5 is a flowchart for explaining the operation of the remote printer 1. In step s1,
The power switch and the like are turned on to start supplying power. In step s2, the power lamp of the display panel 8 is turned on to indicate that the power supply has started.

In step s3, the changeover switch 6 is turned on.
Or OFF. Changeover switch 6
Is ON, the process proceeds to step s4. Since the changeover switch 6 is ON, it is the area R1 of the flash ROM 3 that is read by the CPU 2 immediately after the reset. In step s4, key data input from the input key group 7 is read, and the key data is stored in a key buffer secured in the work area of the RAM 4. The processing based on the key data is performed by the key processing program.

At step s5, it is determined whether or not the key data input from the input key group 7 indicates a program change request. If the request is not a program change request, the operation program in the flash ROM 3 is read and executed. Step s if it is a program change request
Proceed to 6.

In step s6, the program for changing the storage contents of the IPL program is executed, and the flash ROM 3
The IPL program stored in the area R1 is read and written into the area R4 of the RAM 4. In step s7,
It is determined whether or not the changeover switch 6 is OFF. When the changeover switch 6 is OFF, the process proceeds to step s8. Step S7 when the changeover switch 6 is ON.
Is performed.

In step s8, the changeover switch 6 is turned off.
Based on F, the memory map is changed as shown in FIG. 3 (2), and the memory assigned to areas AR1 and AR2 is switched. By the processing in step s8, the CPU 2
It is the region R4 of the RAM 4 that goes to read after reset. In step s9, the I stored in the RAM 4
The storage content changing program of the PL program is executed.

In step s10, the IPL program and the operation program stored in the flash ROM 3 are erased by the currently executed storage content changing program. In step s11, for example, the updated IPL program and operation program supplied from the external computer device are written into the program data reception buffer secured in the work area of the RAM 4 via the RS-232C interface 12. In step s12, the IPL written in the program data reception buffer
The program and the operation program are read and written into the flash ROM 3.

In step s13, the flash ROM 3
It is determined whether the IPL program and the operation program have been accurately written. By comparing the program data written in the flash ROM 3 with the program data stored in the RAM 4, it is determined whether or not the data has been normally written in the flash ROM 3. If the program data has been normally written, the process proceeds to step s14. In step s14, as a normal end process, for example, a predetermined display lamp of the display panel 8 is turned on to indicate that the rewriting has been normally completed, and the buzzer 9
A buzzer sounds from.

In step s15, the changeover switch 6 is turned on so as to refer to the updated IPL program written in the flash ROM 3 when the power is turned on next time. When the changeover switch 6 is turned on, the signal level of each output of the mapping changeover circuit 22 is changed, and the process is completed by defining a memory map as shown in FIG. Since the changeover switch 6 is turned ON, the first address to be referred to by the CPU 2 at the next power ON is the head address of the flash ROM 3.

If it is determined in step s13 that the program data has not been correctly written, the flow advances to step s16. In step s16, it is determined whether or not a third program data write error has occurred. If it is determined that this is the third error, the process proceeds to step s17. In step s17, it is determined that the rewriting of the program data is not performed normally, a predetermined display lamp of the display panel 8 is turned on, a buzzer 9 is intermittently sounded by the buzzer 9, and the end of the error is notified. finish. If it is determined in step s16 that the number of rewrite errors is less than the third time, the process from step s10 is performed.

If an error has occurred, the flash R
Since the IPL program is not written in OM3,
The CPU 2 is reset to start the IPL program stored in the RAM 4 again. At the end of the error, the changeover switch 6 remains OFF and cannot be changed over. Therefore, after the CPU 2 is reset, the processes after step s18 are performed.

If it is determined in step s3 that the changeover switch 6 is OFF, the flow advances to step s18. In step s18, the memory map is changed based on the state of the changeover switch 6. By the processing in step s18, the CPU 2 comes to refer to the area R4 of the RAM 4 at the time of reset. In step s19, a storage content changing program in the IPL program stored in the area R4 is executed.

In step s20, the IPL program and the operation program stored in the flash ROM 3 are erased by the currently executed storage content changing program. Even when the program is reset after the end of the error and the storage content changing program is executed again, the erasing operation of the flash ROM 3 is performed.

At step s21, the updated IPL program and operation program supplied from, for example, an external computer device are written to the program data reception buffer secured in the work area of the RAM 4 via the RS-232C interface 12. . I in RAM4
After the PL program and the operation program have been written, the processing after step s12 is performed.

As described above, according to the present embodiment, when rewriting the IPL program and the operation program stored in the flash ROM 3 in the remote printer 1, a predetermined key in the input key group 7 is operated. As a result, the IPL program including the program for changing the stored contents is written into the RAM 4. RAM
The program for changing the stored contents is executed from the IPL program written in 4 to erase the contents of the flash ROM 3, and the program given via the RS-232C interface 12 is written to the flash ROM 3. Since the storage content changing program for rewriting the storage content of the flash ROM 3 is stored in the flash ROM 3 in which the operation program is stored, a dedicated ROM for storing the storage content changing program is stored in a remote printer. 1, the operation program can be rewritten, and the number of components can be reduced.

When executing the storage content changing program written in the RAM 4, the write protection circuit 23 does not perform writing to the area of the RAM 4 in which the IPL program is stored. The rewriting operation can be performed stably without runaway.

Since the memory referred to by the CPU 2 after the reset is determined by the output of the mapping switching circuit 22 based on the state of the changeover switch 6, an error occurs during execution of the storage content change program. Can be reset and the rewriting process can be performed again.

FIG. 6 shows a flash ROM 33 included in a remote printer 31 according to a second embodiment of the present invention.
FIG. 3 is a block diagram showing the configuration of FIG. Remote printer 31
Is the same as the remote printer 1 except that the flash ROM 3 is replaced with the flash ROM 33, so that the same components are denoted by the same reference numerals and description thereof is omitted.

The flash ROM 33 includes a flash memory cell 41, an ID storage register 42, an ID reference register 43, a comparison circuit 44, and a data protection circuit 45. The flash memory cell 41 is electrically rewritable, and data supplied from the data bus 13 is written only when the write enable signal WRA supplied from the data protection circuit 45 is at a high level, for example. .

The ID storage register 42 is composed of a non-volatile memory such as a PROM, and can write data only once. In the ID storage register 42, for example, ID information predetermined by a manufacturer of the flash ROM 33 is written. The ID information written by the manufacturer is hereinafter referred to as “maker ID information”.

The ID reference register 43 is a register in which ID information input by a user is written, and is formed of, for example, a volatile memory such as a RAM. The ID information written by the user is hereinafter referred to as “user ID information”.
Called. The user ID information is input by using, for example, numerical keys provided as input key group 7 when a user attempts to write data in flash memory cell 41.

The comparison circuit 44 compares each piece of ID information stored in the ID storage register 42 and the ID reference register 43. Each I stored in each register 42, 43
When the D information matches, the match detection signal SA is supplied to the data protection circuit 45. The data protection circuit 45 outputs the write enable signal WRA to the flash memory cell 41 when the write signal WR is supplied from the CPU 2 while the match detection signal SA is being supplied.

FIG. 7 is a flowchart for explaining a process when writing to the flash ROM 33.
When writing to the flash ROM 33, the user inputs user ID information. The input user ID information is stored in the ID reference register 43 via the data bus 13. In step a1, user ID information is stored in the ID reference register 43. The comparison circuit 44 compares the user ID information with the maker ID information stored in the ID storage register 42.

In step a2, as a result of the comparison in step a1, it is determined whether or not the user ID information and the maker ID information match. When the user ID information and the maker ID information match, the process proceeds to step a3. In step a3, the match detection signal SA is supplied from the comparison circuit 44 to the data protection circuit 45, and writing to the flash memory cell 41 is permitted.

At step a4, the coincidence detection signal SA is supplied to the data protection circuit 45, and when the write signal WR is supplied from the CPU 2, the flash memory cell 4
1 is supplied with a write enable signal WRA, and writing to the flash memory cell 41 becomes possible.

As described above, according to the present embodiment, the ID
If data equal to the manufacturer ID information stored in the storage register 42 is not input, the flash memory cell 4
Since data cannot be written in the flash memory cell 1, the contents of the flash memory cell 41 can be prevented from being rewritten carelessly.

[0062]

As described above, according to the present invention, the program for changing the storage contents executed when changing the storage contents of the nonvolatile memory is changed from the nonvolatile memory to the RAM when the operation program is rewritten. Since the program is transferred and executed, it is not necessary to provide a dedicated non-volatile memory for storing a program for changing storage contents in the computer device, so that the number of parts of the computer device can be reduced and the cost of the product can be suppressed.

Further, according to the present invention, the storage content changing program transferred to the RAM is protected by the protection means and is not written, so that the storage content changing program stored in the RAM is not written. When the program is executed, it is possible to prevent the program for changing the storage content stored in the RAM from being rewritten due to noise or the like, thereby preventing the program from running away.

Further, according to the present invention, whether a program is written in a predetermined storage area of the nonvolatile memory is determined by whether or not a change operation is instructed by the change instructing means.
Since a program for changing stored contents stored in the storage area of the RAM is selected, a program in a predetermined area of the nonvolatile memory or the RAM can be read and executed according to a desired operation.

According to the present invention, the electrically rewritable nonvolatile memory in the computer device is
Since the flash EPROM is used, rewriting can be reliably performed even when rewriting is performed in the entire memory area or in units of blocks divided into a predetermined size.

Furthermore, according to the present invention, when changing the storage content of the nonvolatile memory, it is determined whether the data input from the input means matches the protection code stored in the register. Since the protection means determines and permits writing only when the password matches, the storage contents of the nonvolatile memory can be changed only when the same data as the protection code can be input from the input means. In addition, careless rewriting of the stored contents can be prevented.

Further, according to the present invention, when changing the storage content of the nonvolatile semiconductor memory, it is determined whether or not the data input from the input means matches the protection code stored in the register. Since the comparison and protection means judge and allow writing only when they match,
Only when the same data as the protection code can be input from the input means, the storage content of the nonvolatile semiconductor memory can be changed, and the storage content can be prevented from being rewritten carelessly.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a remote printer 1 according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a switching control circuit 5.

FIG. 3 is a diagram for explaining switching control by a switching control circuit 5;

FIG. 4 is a flash ROM in the remote printer 1.
FIG. 3 is a diagram showing an arrangement of programs stored in a RAM 3 and a RAM 4.

FIG. 5 is a flowchart for explaining the operation of the remote printer 1.

FIG. 6 is a block diagram showing a configuration of a flash ROM 33 included in a remote printer 31 according to a second embodiment of the present invention.

FIG. 7 is a flowchart for explaining processing when writing to a flash ROM 33;

[Explanation of symbols]

 1, 31 Remote printer 2 CPU 3, 33 Flash ROM 4 RAM 5 Switching control circuit 6 Switching switch 7 Input key group 8 Display panel 9 Buzzer 10 DIP switch 11 Printer 12 RS-232C interface 13 Data bus

Claims (6)

[Claims] An electrically rewritable nonvolatile memory in which an operation program of a computer device including a storage content changing program is written, a RAM capable of writing and reading storage content, and a nonvolatile memory From RA to RA
M: a program transfer unit for transferring data to M; a change instructing unit for instructing a change operation of the storage content in the nonvolatile memory; Control means for controlling the storage contents of the nonvolatile memory to be electrically rewritten in accordance with the stored contents changing program. A computer device comprising an electrically rewritable nonvolatile memory. 2. The electrically rewritable nonvolatile memory according to claim 1, further comprising a protection unit that performs write protection on the program for changing storage contents transferred to the RAM by the program transfer unit. A computer device comprising: 3. The control means operates according to a program written in a predetermined storage area of the nonvolatile memory when the change instruction is not instructed by the change instructing means, and the change instruction is instructed by the change instructing means. 3. A program processing means according to claim 1, further comprising a program processing means which operates according to a program stored in a storage area of said RAM to which a program for changing storage contents is transferred by said program transfer means. A computer device including an electrically rewritable nonvolatile memory. 4. The nonvolatile memory according to claim 1, wherein said nonvolatile memory is a flash EP.
4. A computer device comprising an electrically rewritable nonvolatile memory according to claim 1, wherein the computer device is a ROM. 5. The non-volatile memory includes a register in which a protection code is stored at the time of manufacture, input means for inputting data when the storage content is changed, and data input to the input means and stored in the register. The electrically rewritable nonvolatile memory according to any one of claims 1 to 4, further comprising a comparison protection means for comparing the protection code with the protection code and permitting change of the stored content only when the protection code matches. A computer device having a memory. 6. An electrically rewritable nonvolatile semiconductor memory, a register in which a protection code is stored at the time of manufacture, input means for inputting data when storage contents are changed, and data and register input to the input means. A non-volatile semiconductor memory including a comparison protection unit that compares a protection code stored in a storage device and allows only a change in the stored content when the two match.