JPS61134852A - Microcomputer - Google Patents

Abstract

PURPOSE:To prevent program runaway by switching forcibly program flow by means of interruption. CONSTITUTION:Program counters 1,5 are operated entirely reversely. After execution of one instruction, the counter 1 is incremented by one 1 and the counter 5 is decremented by one 1. The result is inputted to a comparison discrimination circuit 6, and the content of the program counter 1 and the inverted content of the program counter 5 are compared. When the result of comparison is the same, the program counter 1 is used as the counter for the microcomputer to flow the control of program. If the result of comparison is not the same due to noise or surge, an interruption takes place by an interruption control circuit 2. A program counter control circuit 4 sets the interruption address to the counters 1,5. Thus, a program for countermeasure of runaway has only to be written in the interruption address.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to microcomputers.

[Conventional technology]

Conventionally, microcomputers, as shown in Figure 2,
It has a program counter 1 that controls the flow of programs processed by an internal circuit 3. Conventional microcomputers have only one program counter, which is a binary counter and is automatically incremented (10 l) by the program counter control circuit 4 every time one instruction is executed. The program counter control circuit 4 also operates with the interrupt signal output from the interrupt control circuit 2 to control the contents of the program counter l.

[Problem that the invention seeks to solve]

The above-mentioned conventional system using a microcomputer has the disadvantage that if the program counter l does not operate normally due to some reason such as noise or surge, the program may run out of control.

SUMMARY OF THE INVENTION An object of the present invention is to provide a microcomputer that can eliminate the above drawbacks and forcibly change the flow of a program when the program goes out of control.

[Means for solving problems]

The microcomputer of the present invention includes a plurality of brodarums and
and a circuit that forcibly sets the contents of the counter to a predetermined value.

〔Example〕

Next, the present invention will be explained using the drawings.

FIG. 1 is a block diagram of the main parts of an embodiment of the present invention.

The micro combinator of this embodiment includes a program counter 1 corresponding to a conventional program counter;
The newly added program counter 5 is compared with the content of the program counter 1 and the content of the program counter 5 inverted by the inversion circuit 7, and if they are different, the interrupt control circuit 2 VC judgment signal is sent. 8 and a program Φ counter control circuit 4 that simultaneously controls the initial settings of the program counter 1 and the program counter 5 as 1 interrupt processing. Note that program counter 5 holds a value that is congruent with program counter l, and the operation is 1.
When the command is executed, it is automatically decremented (-1).

Next, the operation of this embodiment will be explained.

The program counter 1 operates similarly to a conventional micro combinator. The program counter 5 operates in exactly the opposite way to the program session counter 1. now,
If the contents of program counter l are 0OIIB,
The content of program counter 5 is a concomplimentary value of 1.
It is 100B.

After executing the l instruction, the program counter increases by 1010.
It becomes 0B, and the program counter 5 is decremented by 1 and becomes 101.
It becomes 1n. Then, the outputs of these detectors are input to the comparison/judgment circuit 6. The output of the program counter 5 is inverted by an inverting circuit 7 and input to a comparison/judgment circuit 6. The comparison/judgment circuit 6 compares the contents of the program counter l and the program counter 50 inversion 4. If the result of comparison t-1 is "same", the program counter lk
The program counter of this microcomputer controls the program flow t14.

Now, if the contents of the program counter 1 and the program counter 5 are different due to noise/surge or the like, the comparison/determination circuit 60 outputs the determination signal 8 and the interrupt control circuit 2 generates 5 interrupts. Program counter control circuit 4 sets one interrupt address to program counter 1 and program counter 5. Therefore, it is sufficient to place one program to prevent runaway at the 5th interrupt address.

〔Effect of the invention〕

As explained above, according to the present invention, a plurality of program counters are provided, and the program is run while being compared, and if the comparison results do not match, the flow of the program is forcibly changed by one interrupt. By having this function, it is possible to realize a micro combinator that can prevent runaway.

[Brief explanation of drawings]

FIG. 1 is a block diagram of essential parts of an embodiment of the present invention. FIG. 2 is a block diagram of the main parts of a conventional microcomputer. l...Program counter, 2...
Interrupt control circuit, 3... Internal circuit, 4...
. . . Program counter control circuit, 5 . . . Program counter, 6 . . . Comparison judgment circuit, 7.
. . . Inverting circuit, 8 . . . Judgment signal.

Claims (1)

[Claims] a plurality of program counters; a comparison judgment circuit that compares the contents of the plurality of program counters and detects that the contents of the plurality of program counters do not have a predetermined relationship; and an output from the comparison judgment circuit that compares the contents of the plurality of program counters; A microcomputer comprising: a circuit for setting the contents of a program counter to a predetermined value.