JPH0225548B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stored program arithmetic device that decodes an instruction word using an instruction decoder and executes arithmetic processing corresponding to the instruction word.

As is well known, as this type of arithmetic device there is a microcomputer in which an accumulator, an instruction decoder, a timing signal generation circuit, etc. are housed in a single LSI chip. This microcomputer has the versatility of being able to perform various types of control simply by changing the stored contents (command words) of the program memory connected to the data bus, so it can be used in game devices, office processing equipment, etc. Widely used.

However, for manufacturers of such microcomputer application equipment, protection measures against imitation or copying of hardware or software have become a major issue.

That is, the hardware itself of recent microcomputers is becoming extremely common.
For this reason, later manufacturers can very easily manufacture products equivalent to or similar to the first manufacturer by simply decoding the contents of the program memory of the application equipment developed by the first manufacturer, and the first manufacturer can easily produce products that are equivalent to or similar to the first maker. Not only are development costs unable to be recovered, but the situation has also resulted in a huge economic blow. For this reason, it has become a major issue for advanced manufacturers to take measures to protect against imitation or copying of the hardware of the entire system, including software.

The present invention has been made in view of these circumstances, and its purpose is to provide a stored program arithmetic device for which it is extremely difficult to manufacture similar or equivalent products.

To this end, the present invention displays specific information on an external display device, inspects this displayed information using a cyclic redundancy method, etc., and only when the inspection result matches predetermined content does a predetermined command word appear. Configure the group to enable decoding operation,
When there is a mismatch, the decoding operation of a specific command word group out of a predetermined command word group is prohibited or changed.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

FIG. 1 is a block diagram showing an embodiment of applied equipment to which the present invention is applied.

In the figure, an LSI-based microcomputer (hereinafter referred to as CPU) 1 is equipped with various circuits including a program counter 10, and is also used to decode instruction words and execute arithmetic processing corresponding to the instruction words. a command decoder 11 that provides control signals to the various circuits described above; and an external cathode ray tube display device 2.
Display control circuit 12 for displaying specific information on
and a built-in comparator that inspects the display signal for displaying the specific information using the cyclic redundancy method, and gives an instruction to prohibit the decoding operation of the instruction decoder 11 if the result does not match the predetermined content. A test circuit 13 is provided.

On the other hand, the data bus of microcomputer 1
The DB and address bus AB are provided with a program memory 3 that stores a series of command words, and a display controller 4 that controls display operations of the display device 2.

In such a configuration, when the power is turned on, the display control circuit 12 generates control command information for causing the display device 2 to display specific information. Then, the command decoder 11 decodes this control command information and generates a control signal for displaying specific information. As a result, specific information is transferred to the display controller 4 via the data bus DB,
The information is displayed on the display screen of the display device 2 by the control operation of the display controller. In this case, the control instruction information for displaying the specific information is the remaining instruction words of the instruction word group of set A that can be executed by the CPU 1, excluding the instruction word group of set B. It is composed of a combination of command words belonging to a group.

On the other hand, when the display of specific information is started, the inspection circuit 13 starts an operation of sequentially reading the display signal DSP in synchronization with the synchronization signal SYNC. Then, when the reading operation of the display signal DSP for one screen is completed,
This display signal DSP is inspected by the cyclic redundancy method, and if the inspection result matches a predetermined value, an instruction to enable decoding of all instruction words of set A is sent to the instruction decoder 11. give to As a result, a series of instruction words stored in the program memory 3 are decoded by the instruction decoder 11, and arithmetic processing corresponding to the instruction words is sequentially executed.

However, if the test result obtained by the cyclic redundancy method does not match a predetermined value, the test circuit 13 gives an instruction to the instruction decoder 11 to prohibit the decoding operation of the set B of instruction words. Therefore, among the series of instruction words stored in the program memory 3, instruction words belonging to the instruction word group of set B are no longer decoded. That is, the arithmetic processing corresponding to the series of instruction words stored in the program memory 3 becomes impossible to execute. In other words, the arithmetic processing corresponding to the series of command words stored in the program memory 3 is executed only after the display control circuit 12 displays specific information. Therefore, it is not possible to easily manufacture similar or equivalent products by simply copying the contents of the program memory 3, and analysis of the internal configuration of the CPU 1 is required.
However, analyzing the internal configuration of CPU 1 requires advanced technology and measuring instruments, and costs equivalent to the development costs must be borne. As a result, it becomes difficult to manufacture similar or equivalent products, and at least the effect of reducing the desire to manufacture them can be expected.

In this case, if the specific information to be displayed on the display device 2 is a unique name such as the development manufacturer's name or product name, as shown in the display image diagram in Figure 3, it will be a complete imitation of the software and hardware. This will make it clear, and we can expect the effect of prohibiting imitation in this respect as well.

Note that instead of prohibiting the decoding operation of the instruction word group of set B, if the decoding mode is changed, for example by changing the addition instruction to an OR instruction, software analysis will become even more difficult and the software will be even better. effect.

In this way, in the present invention, when specific information is not displayed, the decoding operation of a specific command group is prohibited or changed to another mode, so it is possible to easily replace an equivalent or similar application device developed by an earlier manufacturer. cannot be manufactured. Therefore, if applied to applied equipment such as game devices, extremely effective effects will be exhibited.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of an application device to which the present invention is applied, FIG. 2 is a diagram showing a set of instruction words, and FIG. 3 is a diagram showing an example of a display image. DESCRIPTION OF SYMBOLS 1...Microcomputer, 2...Cathode ray tube display device, 3...Program memory, 11...Instruction decoder, 12...Display control circuit, 13...Inspection circuit.

Claims (1)

[Scope of Claims] 1. A stored program arithmetic device equipped with an instruction decoder that decodes instruction words sequentially read from a program memory and outputs a control signal for executing arithmetic processing corresponding to the instruction words, A display control circuit that displays specific information on an external display device by a combination of command words of a command word group excluding a specific command word group among a predetermined command word group; A test circuit that tests the display signal of the specific information is compared with whether or not the test result in this test circuit matches a predetermined content, and when the test result does not match the predetermined content, the above command is executed. A stored program arithmetic device comprising: a comparison circuit that changes the decoding operation for the specific instruction word group among the decoding operations in the decoder. 2. The stored program arithmetic device according to claim 1, wherein the instruction decoder is configured such that decoding operations for a specific group of instruction words are prohibited by a change instruction from a comparison circuit. 3. The stored program arithmetic device according to claim 1, wherein the instruction decoder is configured so that the decoding results for a specific group of instruction words vary depending on a change instruction from a comparison circuit.