JPS6252635A - Data conversion method - Google Patents

Abstract

PURPOSE:To modify a program without altering contents in a ROM by detecting the address of a program to be modified, inhibiting an access to the memory of the program, and reading and executing programs previously stored in other memories. CONSTITUTION:When the program in the ROM 3 is modified, its address is set to an address decoder 4. Simultaneously the address data of a jump destination is set to a data generator 5, and at the same time the modified program is written in a modifying memory 6. When a microprocessor 1 generates an address on an address bus 10, the address decoder 4 detects the generation to generate an output 12, inhibits the access to the ROM 3, simultaneously drives the data generator 5 and outputs the address data of the jump destination, that is, the contents, to the data bus. Then the modified program is executed. According to a jump instruction on the final line of the program in the modifying memory 6, the operation again returns to the address of the ROM 3.

Description

[Detailed Description of the Invention] [Summary] In a system that has a memory circuit that stores a program and in which a microprocessor executes a program supplied from this memory circuit according to an address, it has become necessary to change the program. At the same time, it detects the address of the program, prohibits access to the memory circuit storing the program, reads out a program previously stored in another memory circuit, and replaces it with the original program. Since the processor executes the program, it is possible to change the program without changing the contents of the memory circuit that stores the program.

[Industrial application field]

The present invention provides a control device using a microprocessor.
The present invention relates to a data conversion method that makes it possible to easily change a program stored in a read-only memory (hereinafter referred to as ROM) by controlling address signals generated by a microprocessor.

A device controlled by a microprocessor generally has a memory area consisting of a ROM, and predetermined control is performed by a program stored in the memory area. In such devices, it may be necessary to change the program for testing purposes such as program debugging, but in such cases, such program changes can be easily made. It is requested that

The present invention aims to provide a data conversion method for changing programs that is suitable for such purposes.

[Conventional technology]

Conventionally, when attempting to change part of a program stored in a ROM, the ROM must be replaced with another ROM in which the changed program has been written, or the contents of the ROM must be moved to the same address space. A method is used in which the content is rewritten after replacing the memory with random access memory (hereinafter referred to as RAM).

[Problem that the invention seeks to solve]

However, with the method of replacing ROMs to change programs, it may be necessary to change multiple ROMs depending on the content of the change, and in such cases, the ROMs may have to be replaced several times before the final change. , and when the ROM is a P-ROM that cannot be rewritten, there is a lot of waste. Furthermore, if the ROM is directly soldered to the printed board without using a socket, there is a high possibility that the pattern on the printed board will be cut when the ROM is attached or removed.

On the other hand, if you change the program by replacing the contents of ROM with RAM, you will need a separate means to load the program into RAM, and if you do not have such means, you will not be able to respond immediately. There's a problem.

[Means for solving problems]

FIG. 1 shows the basic configuration of the system of the present invention.

A memory circuit 101 stores programs necessary for control.

A microprocessor 102 performs necessary control by executing a program supplied from a memory circuit according to an address.

Reference numeral 103 denotes an address detection means, which detects an arbitrary address output to the memory circuit.

104 is a program changing means which prohibits access to the memory circuit when this address is detected, and supplies a program previously stored in another memory circuit to the microprocessor in place of the program in the memory circuit 101. .

[For production]

In the data conversion method of the present invention, in a system where a microprocessor executes a program stored in a memory circuit, when an address of a program that requires modification is detected, access to the memory circuit storing the program is disabled. In addition, the microprocessor jumps to another memory circuit, reads the program stored in that memory circuit, and executes it, making it possible to change the program without changing the contents of the original memory circuit. becomes possible.

〔Example〕

FIG. 2 shows the configuration of an embodiment of the present invention, in which 1 is a microprocessor, 2 is a RAM, 3 is a ROM for storing programs, 4 is an address decoder, 5 is a data generator, and 6 is a A memory for modification is shown, 10 is an address bus, 11 is a data bus, and 12 is an address decode output.

In FIG. 2, the microprocessor 1 normally sequentially specifies the addresses of programs written in the ROM 3 via the address bus 10, and executes the programs read from the ROM 3 onto the data bus 11. is under control.

The middle RAM 2 is used for the microprocessor I arithmetic processing at this time.

If you want to change a certain program currently written in ROM3, enter the address A of the program to be changed.
o is set in the address decoder 4, jump destination address data ao is set in the data generator 5, and
The modified program is written in the modification memory 6.

When the microprocessor 1 generates this address Ao on the address bus 10, the address decoder 4 detects this and generates an output 12 to prohibit access to the ROM 3 and drive the data generator 5. It points to a certain area of the jump prehistory memory 6, which is its contents, and therefore, this part is accessed and the modified program written in advance is read onto the data bus 11, so that the microprocessor 1 runs this program. The last line of the program in the change memory 6 contains a jump command and the jump destination address B.
o is written and when this is read, address B
Since o points to ROM3, the address returns to ROM3, and microprocessor 1 continues to read R.
Execute the OM3 program.

In this case, if a plurality of address decoders and data generators are prepared and the capacity of the change memory is increased to a certain extent, it is possible to change the program multiple times.

When the desired result is obtained by changing the program in the ROM and executing it in this way, it is sufficient to create a new one with the contents of the ROM rewritten and replace it.After that, the address decoder 4 in FIG.゜Data generator 5. The modification memory 6 can be removed.

〔Effect of the invention〕

As explained above, according to the data conversion method of the present invention,
In a system where a microprocessor executes a program that has already been completed and is stored in a memory circuit consisting of ROM, when a program change becomes necessary, it detects the address of the program that requires the change and executes the program. In addition to prohibiting access to the memory circuit that stores the ROM, the microprocessor reads out programs previously stored in other memory circuits and executes them, without changing the contents of the memory circuit consisting of the ROM. , program changes can be easily made.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the basic configuration of the system of the present invention, FIG. 2 is a diagram showing the configuration of an embodiment of the present invention, and FIG. 3 is a diagram showing an example of the contents of the change memory. 1-.-Microprocessor, 2-.-Random access memory (RAM), 3-
Read-only memory (ROM), 4-address decoder, 5-data generator, 6゛...-memory for change, 10-address bus, 11-data bus, 12-address decode output

Claims (1)

[Scope of Claims] In a system that includes a memory circuit (101) storing a program and in which a microprocessor (102) executes a program supplied from the memory circuit according to an address, an arbitrary value for the memory circuit (101) is provided. an address detecting means (103) for detecting the address of the memory circuit (101), which prohibits access to the memory circuit (101) when the address is detected, and executes a program previously stored in another memory circuit. ) A data conversion method characterized by comprising a program changing means (104) for supplying the program to the microprocessor in place of the program.