JPS6083157A - One chip microcomputer - Google Patents

Abstract

PURPOSE:To prevent the decoding of program contents by delivering the program contents to outside after converting the data of a program memory. CONSTITUTION:When a signal is supplied from outside to indicate the reading of contents of a program memory 12, a cipher code set previously to a code generator 16 is applied to an instruction decoder 11. While the address data corresponding to a desired address of the memory 12 is applied via an input/output port 14 to designate an address. Then the data on the address is fetched to an accumulator 11B and converted by the cipher code. In this case, an instruction proper to a microprocessing unit 11 is executed by means of the hardware of the unit 11 itself.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a one-chip microcomputer that can hide the contents of a program memory.

[Technical background of the invention and its problems]

Recently, one-chip microcontrollers have been widely used, which integrate a processing unit, a program memory, and an input/output interface into a single chip and operate as a computer by itself.

FIG. 1 is a block diagram showing an example of such a one-chip microcomputer.

1 in the figure is a microprocessing unit that decodes the nologogram and performs processing according to its contents. Therefore, this microprocessing unit 1 includes an instruction decoder 7A that interprets the instruction part of the program, an akinemulator IB that stores data, a temporary register iC, and an arithmetic and logic operation that operates on the data stored in these. Units □) JD etc. are established. 2
is an f0 gram memory storing 7#p grams, for example, a mask ROM. Furthermore, temporary backup of 3L data,
A RAM is used as a work area, etc., and 4 is an input/output board. Micro Derocessing Units) J,! Near'log 2, RAM 2, RAM 3 and input/output n? −
At n:: with port 4, data is transferred via path 5. and store *f in program memory 2.
'l Program with instruction code 11
Interpret it with dogjutsu logic>1. Controls @ calculation in unit 10. Then, the number a is sent and received to the outside via the input/output port 4 and the Kiheki 1 of this performance.

However, if such a microcolumn is constructed in one chip, the total number of connection points will be significantly reduced. Moreover, the path connecting each unit can be shortened, and the load capacity can also be reduced, so the dimension of the driver circuit can be reduced. Therefore, power consumption can be reduced, heat generation can be reduced, and reliability can be improved by reducing the number of connection points.

Furthermore, since the cost of such a one-chip microcomputer is low, it can be used in various electrical products, for example, which were previously thought to be difficult to control due to the cost. . As a result,
By performing computer control, it becomes possible to perform complex control in response to condition judgments and external inputs. It becomes possible to replace the hardware with software. θ (Ute) can reduce the cost of hardware, and can also change the product specifications by modifying the software without changing the hardware, increasing the flexibility of multi-functions. I can do it.

In such a microprocessing unit, a program is written as a set of instructions, and the instructions are written based on instruction code specific to the processing unit.Also, the user can freely develop a program, and the program can be written as a set of instructions. The instruction code is often made public so that the program can be easily improved. Therefore, if the contents of the program memory can be read out, it becomes possible to easily decode the program and learn the software algorithm.

By the way, some one-chip microcomputers are designed so that the stored contents of the program memory can be read from the outside in order to verify the contents of the program memory. In this type of device, for example, a signal is given from outside to instruct the reading of the contents of the program memory,
By specifying a desired address through the input/output port 4, the contents of the program memory corresponding to the address are outputted through the input/output port 4.

However, in such a case, the program memory 2
Since the contents stored in the computer can be easily read by outsiders, the contents cannot be kept secret. For this reason, an outsider can read and decode the contents of the program memory and easily imitate or improve the contents and use them for his own purposes.

On the other hand, there are some one-chip microcomputers that prevent the contents of the program memory from being read externally, but such devices have the problem of not being able to verify the contents of the program memory during shipping tests, acceptance wiping, etc. there were.

Furthermore, it is conceivable to use a unique non-membrane code as the instruction code for the microprocessing unit 1, but in this case, the program would have no versatility at all, and an already developed zologram would have to be reused. Or, it would be impossible to improve it and use it, which would be unreasonable.

[Purpose of the invention]

The present invention was developed in view of the above circumstances, and it is an object of the present invention to provide a one-chip microcomputer that prevents outsiders from decoding the contents of the program even if the contents of the program memory are read. .

[Summary of the invention]

The present invention is characterized in that, when outputting the contents of the program memory to the outside, the data in the program memory is subjected to data conversion before being outputted to the outside.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described in detail with reference to the block diagram shown in FIG. In this embodiment, an example in which data conversion is performed using an arithmetic and logic unit provided in a microprocessing unit will be described.

In the figure, 11 is a microprocessing unit that interprets the instruction part of the program: In-decoder 11A1 Accumulator 11B1 that stores data 11C1 Temporary register 11C1 Arithmetic and logic operation unit that performs operations on the data stored in these units (ALU: l 1
1D etc. are provided. A program memory 12 stores a program, and is, for example, a nonvolatile read-only memory such as a mask ROM. 13 is a RAM used as a temporary data saver, work area, etc., and 14 is an input/output port. Data is transferred between the microprocessing unit 11, the program memory l 2 , the RAM 13, and the input/output port 14 via the bus 15, and these are integrated into one chip as shown surrounded by broken lines in the figure. It is accumulating.

16 is a code generator. When a signal instructing to read the contents of the program memory 12 is given from the outside,
An encrypted code set in advance in this code generator 16 is given to the instruction decoder 1). Address data corresponding to a desired address of the program memory 12 is inputted via the universal output 7-to 14 to designate the address, and the data at the address is transferred to the accumulator 11.
Import into B. Then, data conversion specified by the encryption code is performed on the data stored in the accumulator IIB. The method for this data conversion is as follows:
Instructions specific to the microprocessing unit 11 may be executed using the hardware of the microprocessing unit 11 itself. Among the instructions that can perform such data conversion, the general microprocessing unit 11 is biased toward A, for example, a shift instruction that shifts the bit position of data, a rotate instruction that rotates the bit position of data, and an inversion instruction that inverts data. There are complement instructions etc. Note that when executing a shift command or a rotate command, the data movement direction and movement amount may be specified arbitrarily. Further, when executing a complement instruction, the bit position to be inverted may be specified.

The data read from the program memory 12 can then be converted and output from the input/output port 4.

If this is done, the data output from the output port 4 will be different from the contents stored in the program memory 12, making it impossible to decipher the program.

For example, as shown in FIG.
IF, E7 in base numbers. Assume that C4 and 8-bit data are stored respectively.

Here, when outputting data to the outside, if you rotate it to the right by one pit, the addresses (N = 1) and (
N) The value of (N+1) is 8F, F3.

92 and output. Therefore, the contents of the data stored in the program memory 12 cannot be known at all from the data output to the outside.

Therefore, the program stored in the program memory 12 can be zologrammed using instruction codes specific to the processing unit 1. Therefore, already developed programs can be used as they are, and these programs can be easily improved. Furthermore, in the case where a mask ROM is used as the program memory 12, the ROM portion can be created using the conventionally used mask as is, and its contents can be kept secret.

That is, when reading the contents of the program memory 12 to the outside, the data is converted based on the code input from the code generator 6. For this reason, an outsider who does not know the data conversion method cannot decipher the read program, and therefore the contents of the program can be kept secret. Conversely, by knowing the program conversion method, the original program can be restored from data read using the reverse method, and its contents can be easily analyzed.

Note that the present invention is not limited to the above-mentioned embodiment, and in the above-mentioned embodiment, an instruction code specific to the microzoro processing unit 11 is used and the data conversion is performed using the hardware. Dedicated hardware for data conversion may also be provided. Furthermore, when data is to be output from a specific input/output port, hardware for performing such data conversion may be provided at the port and operated only when outputting the contents of the program memory.

FIG. 6 is a block diagram showing an example of such a one-chip microcomputer, in which code conversion means is provided at the output port. That is, in FIG. 6, a code converter 6 is provided at an output port for outputting the contents of the program memory 2 to the outside, so that the contents of the program memory are subjected to code conversion and output.

FIG. 4 is a diagram showing the internal block of 18048 (model number, In'chill Co., Ltd.), which is widely used as a one-chip microcomputer. This one-chip microcomputer has an IK-byte mask ROM 10J, a 64-byte RAM z02, and three sets of 8-bit input/output capacitors (10JA, 103B).

103C and an instruction decoder 10
4, a micro processing unit 104 consisting of a temporary register 104B + an accumulator 104C, an arithmetic logic unit 104D, etc. is connected to an internal bus 105.
These are interconnected and integrated into a single chip.

and mask ROM used as program memory
To read the contents of J01, connect +12 to the external address select terminal FA of the control and timing circuit 106.
By applying V and giving address data from the data buses DBII) to DB7 and the lower two pits of the input/output port 103c, the contents of the mask ROM 101 corresponding to the address are outputted via the data buses DBO to DB7. I try to do that.

However, when the present invention is applied to this Wanchizo microprocessor, for example, as shown in the block diagram of FIG.
A code generator 107 is provided between the code generator 4 and the code generator 107. And mask ROM 10 for external address select terminal EA.
According to the instruction to read the contents of J, the programmable ROM 101
The data read from the code generator 107 undergoes code conversion as instructed by the code given from the code generator 107, and is output from the data buses DBO to DB7. That is, from the above code generation f51oy to l'ii 80
The instruction decoder 104 outputs a predetermined code according to the instruction code 48.
data conversion. Therefore, data conversion can be performed in the same way as normal program execution using hardware specific to the 18048, and hardware improvements can be made only in areas related to the code generator 107, making it extremely easy to implement. can.

〔Effect of the invention〕

As described above, the present invention performs data conversion on the contents of the program memory and outputs the data to the outside, so that the program cannot be decoded, and furthermore, by performing data conversion in reverse, the original program can be easily restored. The generality of the contents of the zologram memory is not compromised, and the
- It is possible to provide a one-chip microcomputer with few additional hardware parts.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a conventional one-chip microcomputer, FIG. 2 is a block diagram showing an embodiment of the present invention, FIG. 3 is a diagram explaining an example of data conversion in the above embodiment, and FIG. Figure 4 is a block diagram showing the 18048 type one-chip micro converter, and Figure 5 is the +80 type.
FIG. 6 is a block diagram showing an example in which the present invention is applied to a 48-inch one-chip microcomputer, and FIG. 6 is a block diagram showing still another embodiment of the present invention. 11...Microgrossing unit, 12...
・Program memory, 13...RAM, 14...I/O J? -t, 15...bus, 16...code generator. Applicant's agent: Takehiko Suzue, Patent attorney, Figure 3: De-Yu, Mota, Director of the Patent Office, Kazuten Wakasugi, Indication of the case, Patent Application No. 191915-1982, Name of the invention: One-chip micro Relationship between computer 3 and person making amendment 4f Patent applicant (307) Tokyo Shibaura Electric Co., Ltd. 4, agent 5, voluntary amendment (1) Same page as "ru." on page 13, line 2 of the specification Insert the following between the third line and "This invention". Furthermore, the encryption code for the program memory 12 and the code generator 16 can be manufactured in the same process. In this way, the number of steps for manufacturing the encrypted code will not be increased, and the encrypted code can be set for each content of the program memory 12, which is reasonable. (2) Add the following to the second line of page 16 of the same book, after "It can be done." Note that a mask ROM containing a predetermined program is used.
If the encryption code of the code generator 1θ6 is simultaneously manufactured in the manufacturing process of 101, there is no need to provide a special process for manufacturing the encryption code, and the mask ROM 10
A different encryption code can be easily set for each content of I.

Claims (1)

[Scope of Claims] (1) A program memory that stores a program, a microprocessing unit that executes the program read from the program memory, and an input that inputs or outputs data operated by the microprocessing unit to the outside. A one-chip microcomputer comprising an output port and means for converting codes when outputting the contents of the program memory to the outside. Q) A one-chip microconverter according to claim 1, characterized in that code conversion means is provided at an output port for outputting the contents of a program. (3) A program memory that stores a program, a microprocessing unit that executes the program read from this program memory and converts the code when outputting the contents of this program to the outside, and operations performed by this microprocessing unit. A one-chip microconbeater equipped with an input/output port for inputting or outputting data to the outside. (4) Permissible scope of claim 3, characterized in that the data conversion in the microprocessing unit is performed by hardware specific to the microprocessing unit using an instruction code that is preprogrammed as an encryption code. One-chip microcontroller. (5) A one-chip microcomputer according to claim 4, characterized in that the encryption code is provided in the same process as the program memory. (6) The microprocessing unit according to claim 4, wherein the data conversion involves rotating data read from the program memory by a predetermined value. (7) The microprocessing unit according to claim 4, wherein the data conversion involves inverting predetermined bits of data read from the program memory.