JPH01207862A - Program destruction detecting circuit - Google Patents

Abstract

PURPOSE:To attain the early discovery of a program destruction and the detection of a destructive bit position and to improve the maintainability of the program by compare-collating a calculated check sum value and a stored check sum value with an exclusive OR system. CONSTITUTION:The check sum value of a program part obtained by a check sum circulator 1 and a check sum value read out of a check storage circuit 2 are inputted to a check sum comparison circuit 3. The circuit 3 collates with the exclusive OR system, outputs zero when both sum values are equal and, otherwise, outputs a figure other than the zero. The output of the circuit 3 is displayed on the check sum indicator 4. Consequently, the presence or non- presence of the program destruction and the position of the destruction can be visually checked. Thus, the early discovery of the destruction, the improvement of the reliability of the detection and the detection of the destructive bit position are attached and the maintainability of the program is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a program corruption detection circuit used for software maintenance, which improves program maintainability.

[Conventional technology]

FIG. 2 is a block diagram showing a conventional program corruption detection circuit. In the figure, 1 is a checksum calculator that calculates the checksum of the program section, and 4 is a checksum value calculated by the checksum calculator 1. It is a checksum indicator.

Next, the operation will be explained. FIG. 3 is a diagram for explaining a checksum, where 31 is a memory address and 32 is data. Data 32 at memory address 31 is transferred to the second
The result is input to the checksum calculator 1 shown in the figure to obtain an arithmetic addition value.

Arithmetic addition here means arithmetically adding the MSB (the most significant bit of the word) as a sign bit. When obtaining the checksum for every four words of the memory address, the corresponding data of four consecutive words are arithmetic added in FIG. The checksum value 33 that has been determined is notified to the operator using the checksum display 4 shown in FIG.

The operator compares and checks this checksum value 33 with a previously calculated checksum value to check for program corruption and the location of the corrupted bit.

[Problem to be solved by the invention]

The conventional program destruction detection circuit is configured as described above, and the checksum display value directly displays the calculated checksum value, so the judgment of normality/abnormality (-program destruction) is performed by visual inspection by the operator. Was.

Therefore, the number of bits per word is 4 bits → 8 bits →
If the number of bits increases from 15 bits to 32 bits, there are problems such as the burden on the operator due to visual inspection and the risk of overlooking program destruction due to uncertainty.

This invention was made in order to solve the above-mentioned problems, and provides a program destruction detection circuit that can eliminate the burden on the operator caused by visual inspection and the uncertainty caused by visual inspection, and shorten the visual inspection time. The purpose is to provide.

[Means to solve the problem]

The program destruction detection circuit according to the present invention compares and verifies the calculated checksum value with the stored checksum value using an exclusive OR method, and informs the operator of the presence/absence of program destruction and the location of the destruction pin 1. This is to let you know.

[Effect]

In this invention, the calculated checksum value and the stored checksum value are compared and verified using an exclusive OR method, so when the verification result is zero, the program is normal, and the verification result is zero. If not, it is possible to know the program destruction and its destruction bit position.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a program corruption detection circuit according to an embodiment of the present invention.
3 is a checksum storage circuit that stores the program checksum value, and 3 is a checksum value calculated by the checksum calculator 1 and the checksum value stored in the checksum storage circuit 2 using an exclusive OR method. A checksum comparison circuit 4 is a checksum display device that displays a checksum value based on the comparison result of the checksum comparison circuit 3.

Next, the operation will be explained. The checksum value of the program section obtained by the checksum calculator 1 shown in FIG. 1 and the checksum value read from the checksum storage circuit 2 are input to the checksum comparison circuit 3. The checksum comparison circuit 3 employs a comparison verification method using exclusive OR. The relationship between the two-manpower of this exclusive OR and the output is shown in the table below.

In the table, input 1 corresponds to the checksum value of checksum calculator 1, and input 2 corresponds to the checksum value of checksum storage circuit 2. In this way, if the checksum value of the checksum calculator 1 and the checksum value of the checksum storage circuit 2 are the same value, the output of the checksum comparison circuit 3 is “
If the checksum value of the calculator 1 and the checksum value of the storage circuit 2 are not the same value, the output of the comparator circuit 3 will be other than 0pa.

The output of this checksum comparison circuit 3 is displayed on a checksum display 4. This display directly shows the presence or absence of program corruption (whether there is a non-zero display) and the position of the abnormal bit (non-zero display position), allowing the operator to easily identify program corruption by visual inspection. /Absence and abnormal bit positions can be detected.

In this way, in this embodiment, the output of the checksum calculator and the output of the checksum storage circuit are compared and verified by the checksum comparison circuit using the exclusive OR method, and the result is displayed on the checksum display, so that the operator can Since it is now possible to easily visually inspect the presence or absence of program corruption and the bit position of the program corruption, the operator's burden and the uncertainty of detection due to visual inspection can be eliminated, and the visual inspection time can be significantly shortened. .

〔Effect of the invention〕

As described above, according to the present invention, since the calculated checksum value and the stored checksum value are compared and verified using the exclusive OR method, program corruption can be detected early and detected with certainty. improvement.

This makes it possible to detect the location of broken bits, which has a great effect on improving the maintainability of programs.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a program destruction detection circuit according to an embodiment of the present invention, FIG. 2 is a block diagram showing a conventional program destruction detection circuit, and FIG. 3 is a diagram for explaining a checksum. 1 is a checksum calculator, 2 is a checksum storage circuit,
3 is a checksum comparison circuit, 4 is a checksum display device,
31 is a memory address, 32 is memory data, and 33 is a checksum value. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) A checksum calculation circuit that calculates the checksum value of a program, a checksum storage circuit that stores the checksum value of the program, and a checksum comparison circuit that compares both of the above checksums using an exclusive OR method. A program destruction detection circuit characterized by comprising: