JPH04235650A - Microcomputer with built-in memory - Google Patents

Abstract

PURPOSE:To prevent the illicit copying or analyzing operation of the data or the programs written in a built-in memory of a microcomputer. CONSTITUTION:A central processing unit(CPU) 2 reads the data and programs out of an external memory (EPROM) 11 based on a write program stored in a storage device 12 and writes them in a built-in memory (EPROM) 3 in a write mode where the data and programs are written into the memory 3. Thus the data and programs can be written into the memory 3 by the CPU 2 with the write program and therefore the contents of the memory 3 are never read out to the outside. As a result, the outsiders except the producer or the due users of a microcomputer can never illicitly copy or analyze the data and the programs stored in the memory 3.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microcomputer with a built-in memory including an erasable and programmable read-only memory (EPROM, etc.).

0002

[Prior Art] In a conventional microcomputer with a built-in memory, for example, a microcomputer with a built-in EPROM, data is written to and read from the built-in EPROM under control from outside the microcomputer (hereinafter simply referred to as external). was.

FIG. 3 is a block diagram showing the main part configuration of such a conventional microcomputer with a built-in EPROM. In FIG. 3, 1a is a microcomputer with a built-in EPROM of this conventional example, which includes a central processing unit (hereinafter referred to as CPU) 2 that performs calculations and controls for processing data;
It is composed of a built-in EPROM 3 as a built-in memory that stores data and programs for operating the CPU 2, an input/output port 4a for inputting and outputting, and an internal bus 5. Vpp is the program voltage, Vcc is the power supply voltage, V
ss represents a ground potential, 8 is a program voltage input terminal, 9 is a power supply voltage input terminal, and 10 is a ground terminal. 6a is an external address bus, and 7a is an external data bus.

FIG. 4 shows data stored in the built-in EPROM of this conventional example.
A flowchart showing the procedure for external control when writing data.
Figure 5 is a flowchart showing the procedure for external control when reading data from the built-in EPROM.
It is.

The operation of this conventional example will be explained below with reference to FIGS. 3 to 5.
Explain according to the following. When writing data to the built-in EPROM 3, the flowchart in FIG. 4 is followed. In step 1, the program voltage input terminal 8 and the power supply voltage input terminal 9 have a program voltage (Vpp) and a power supply voltage (Vcc).
is applied (step S41), and the ground terminal 10 is directly connected to the ground potential (Vss). Further, an initialization address (for example, the start address of the built-in EPROM) is input from the external address bus 6a to the input/output port 4a (step S42). The above is stage 1. Stage 2
Then, the data to be written is input from the external data bus 7a to the input/output port 4a, and the input/output port 4a transmits the data to the built-in EPROM 3 via the internal bus 5. The built-in EPROM 3 writes the received data to the address specified in step S43 of stage 3, which will be described later (step S44).

[0006] Next, in order to check whether writing has been performed normally, the built-in EPRO
The data stored at the address of M3 is read out via the internal bus 5 and the input/output port 4a (step S45).
). Writing, reading, and checking are repeated until the write data and read data match (step S46). The above is stage 2. In step 3, the address input from the preset address bus 6a is sent to the built-in EPRO via the input/output port 4a and the internal bus 5.
M3, and in this state step 2 is executed. Stage 2
After completion of , the address is incremented (step S47) and address specified (step S48) until the address reaches the end address of the built-in EPROM 3 (step S48).
43), repeat the execution of step 2. This completes the write operation.

When reading data from the built-in EPROM 3, the flowchart shown in FIG. 5 is followed. In step 1, a program voltage (Vpp) necessary for reading is applied to the program voltage input terminal 8, a power supply voltage (Vcc) is applied to the power supply voltage input terminal 9 (step S51), and the ground terminal 10 is directly connected to the ground potential. be done. Further, as in the case of writing, an initialization address is given from the address bus 6a to the input/output port 4a (step S52). The above is stage 1. In step 2, the address input from the address bus 6a is given to the built-in EPROM 3 via the input/output port 4a and the internal bus 5 (step S
53). The built-in EPROM 3 outputs the data stored at the given address to the external data bus 7a via the internal bus 5 and the input/output port 4a (step S54).
). Next, the address given from the external address bus 6a is incremented (step S55), and address designation and data reading are repeated until the address becomes the end address of the built-in EPROM 3 (step S5).
6).

[0008]

[Problem to be Solved by the Invention] Since the conventional microcomputer with a built-in EPROM is configured as described above, data or programs written in the built-in EPROM can be easily read out with a general-purpose EPROM writer, etc. Therefore, there is a problem in that data and programs can be illegally copied or analyzed by a third party other than the microcomputer manufacturer or the authorized microcomputer user.

[0009] This invention was made to solve the above-mentioned problems, and includes a built-in memory (EPROM) that can prevent data and programs written in the internal memory (EPROM) from being illegally copied or analyzed. The purpose is to obtain a microcomputer.

0010

[Means for Solving the Problems] A microcomputer with a built-in memory according to the present invention has a built-in memory (built-in EPROM).
3) Prepare in advance an external memory (external EPROM 11) that stores data and programs to be written to the internal memory, and operate the central processing unit 2 in the mode for writing data and programs to the internal memory to write data and programs to the external memory. It is equipped with a storage device 12 that stores a writing program for writing contents into the built-in memory.

[0011]

[Operation] When in the mode of writing data and flowcharts into the built-in memory (built-in EPROM 3), the central processing unit 2 stores data and flowcharts into the external memory (external EPROM 11) according to the writing program stored in the storage device 12. The day that was done
data and programs and write them to the built-in memory.

0012

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing the main structure of a microcomputer with a built-in memory, for example, a microcomputer with a built-in EPROM, according to an embodiment of the present invention. Figure 1
Components corresponding to those shown in FIG. 3 are given the same reference numerals, and their explanations will be omitted. In Figure 1, 1
b is a microcomputer with built-in EPROM of this embodiment, and 12 is a built-in E provided in the microcomputer 1b.
6b is a storage device storing a writing program for operating the CPU 2 and writing the contents of the external memory prepared in advance to the built-in EPROM 3 when in the mode of writing data and programs to the PROM 3; 7b is a data bus that connects to the input/output port 4b from the outside, 13 is a write end signal that is output from the input/output port 4b to the outside, and 11 is a built-in EPR.
This is an external EPROM that stores data and programs to be written into the OM3 and serves as an external memory.

FIG. 2 shows the data stored in the built-in EPROM of this embodiment.
Fig. 3 shows a flowchart for writing data.

Next, the write operation in this embodiment will be explained using FIGS. 1 and 2. In the write operation start process, a program voltage (Vpp) is applied to the program voltage input terminal 8 and the power supply voltage input terminal 9, respectively.
and the power supply voltage (Vcc) are applied (step S21).
, the ground terminal 10 is directly connected to the ground potential (Vss). In this state, the writing program in the storage device 12 is executed by the CPU 2 (step S22). In phase 1, external address bus 6b is connected to external EPRO
Initialized to specify the start address of M11 (
Step S23). Then in step 2 the external EPROM
11 outputs the data to be stored at the address designated by address bus 6b to data bus 7b. CPU2
receives the data via the input/output port 4b and the internal bus 5 (step S24), and writes the received data to a predetermined address in the built-in EPROM 3 (step S25). CPU2 further immediately beforehand writes the data (WRDAT
Data is read from the address where A) was written (step S26), and the write data (WRDATA) is read.
and read data (RDDATA) (step S27), and repeat writing, reading, and comparison until they match.

In step 3, after executing step 2, the address specified by the address bus 6b is incremented (step S28), and until this address becomes the final address of the EPROM 11 (step S29), the execution of step 2 and the address increment are continued. repeat. In stage 4, CPU2
outputs the write end signal 13 via the internal bus 5 and input/output port 4b (step S30). Externally, the completion of the write operation is known by the generation of the write end signal 13.

As described above, in this embodiment, the built-in EPR
When writing data to OM3, there is no need for external control such as address designation. Although EPROM is used as the built-in memory and external memory in the above embodiment, the present invention is not limited thereto.

[0017]

As described above, according to the present invention, a writing program for operating the central processing unit and writing the contents of external memory to the internal memory when in the mode of writing data or programs to the internal memory. Since it is configured with a storage device for storing data, data and programs can be written to the built-in memory by the operation of the central processing unit by the writing program, and the contents of the built-in memory cannot be read externally. Therefore, it is possible to prevent illegal copying and analysis of data and programs in the built-in memory by a third party other than the manufacturer of the microcomputer and the user of the microcomputer.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the main part configuration of a microcomputer with a built-in memory according to an embodiment of the present invention.

FIG. 2 is a flowchart for explaining a write operation in this embodiment.

FIG. 3 is a block diagram showing the main part configuration of a conventional microcomputer with built-in memory.

FIG. 4 is a flowchart for explaining a write operation in this conventional example.

FIG. 5 is a flowchart for explaining a read operation in this conventional example.

[Explanation of symbols]

1b Microcomputer with built-in EPROM (microcomputer with built-in memory) 2 Central processing unit 3 Built-in EPROM (built-in memory) 11 External EPROM (external memory) 12 Storage device

Claims (1)

[Claims] Claim 1: A microcomputer with built-in memory, comprising a central processing unit that performs calculations and control for processing data, and a built-in memory that stores data and programs for operating this central processing unit. - In the computer, prepare in advance an external memory storing data and programs to be written to the built-in memory, operate the central processing unit when in the mode for writing data and programs to the built-in memory, and write the data and programs to the built-in memory. A microcomputer with a built-in memory, comprising a storage device storing a writing program for writing the contents of an external memory into the built-in memory.