JPH03166689A - Program checking method - Google Patents

Abstract

PURPOSE:To securely check the contents of a program and to prevent the runa way due to program error by executing the sum check of the entire area of the program in a RAM and judging whether or not the program in the RAM is effective or ineffective. CONSTITUTION:When the power source is turned ON with a control switch turned OFF while the loading of the program to the RAM is incomplete, the contents of a memory for inspection are read in and the sum check value of the program in the RAM is calculated and compared with a sum check value in a memory for inspection. When the power source is turned ON with the control switch turned ON, the program is loaded in the RAM and the sum check value of the program in the RAM is calculated. The start address, size, and sum check value of the program in the RAM are written in the memory for inspection and the program in the RAM operates normally. When the power source is turned ON with the control switch turned OFF while the program loading to the RAM is complete, the program in the RAM begins to be executed. Consequently, the program is prevented from running away owing to a program error.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is a program for a microcomputer system used in electronic registers, POS systems, NC-controlled III devices, etc. in which application software operates on RAM (writable memory). Please check the check method.

Prior Art In this type of microcomputer system, RA
If it is possible to execute a program in RAM without loading the program into M, in order to check whether the program in RAM is valid or not,
A method has been adopted in which a specific pattern is written in a specific memory when the RAM program is read into the RAM after the power is turned on, and then the pattern is checked if the RAM program is not read into the RAM.

Problems to be Solved by the Invention In the conventional method of checking such a memory, the RA
Although this is effective in checking whether the M program has been loaded, it cannot guarantee the contents of the program in RAM. That is, even if a specific pattern in a specific memory is stored correctly, other parts may have changed from their original values, and in that case, it is conceivable that a major failure will occur in the microcomputer system.

In view of the problems of the prior art, it is an object of the present invention to provide a program checking method that can reliably check the contents of a program and prevent runaway.

Means for Solving the Problems The present invention includes a ROM, a RAM, and a test memory,
After the power is turned on, the program in the ROM is transferred from the outside to the RA.
When reading a program into R, control is transferred to the program in the RAM, and then the program in the RAM is read into the R.
If the start address, size, and sum check value of the AM program are stored in the test memory, and the program in the ROM does not read a program from the outside into the RAM after power is turned on, the program in the ROM is stored in the test memory. A sum check value of the program in the RAM is calculated based on the start address and size of the program in the RAM in the memory, and is compared with the sum check value in the test memory. If they match, control is executed to the program in the RAM. This is a program check method characterized by transferring the data and determining an error if there is a mismatch.

Operation As described above, the present invention performs a sum check on the entire area of the RAM program, and as a result, determines whether the RAM program is valid or invalid, so even if a portion of the RAM program changes, it can be reliably grasped. If the sum check values do not match, control is not passed to the program in the RAM and an error occurs, thereby preventing damage to the microcomputer system due to program runaway.

Example Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a flowchart showing an embodiment of the program checking method of the present invention.

Among these, step Sl, step S2, step S3, step S6, step S7, and step S8 are R
It is executed by a program in OM (read-only memory),
Steps S4 and S5 are executed by a program in RAM.

(1) When the power is turned on with the control switch in the OFF state with the program loading to the RAM incomplete: The control switch is read in step Sl, the control switch is checked to see if it is on in step S2, and the control switch is turned off. Since it is off, the contents of the test memory are read in step S6, and the sum check value of the program in the RAM is calculated in step S7. Then, in step S8, it is compared with the sum check value in the test memory. Naturally, the sum check will not match, resulting in an error. Note that if a certain limit is set on the start address and size of the program in the RAM, it is possible to detect an error by checking the limit.

(2) When the power is turned on with the control switch in the ON state: The process proceeds to step St and step S2, and since the control switch is on, the program is loaded into the RAM in step S3. Then, in step S4, the sum check value of the program in the RAM is calculated. In step S5, the start address, size, and sum check value of the program in the RAM are written into the test memory.

In this way, the program in the RAM operates normally. Here, the process of loading the program into the RAM in step S3 is performed through a communication line, which requires time and the line usage fee is high, so this process cannot be used frequently. Therefore, in order to execute the program in the RAM without performing the process of loading the program into the RAM in step S3, preparations are made in steps S4 and S5 to guarantee the operation at that time, as described above. Needless to say, the RAM is backed up by a battery.

(3) When the control switch is turned off and the power is turned on with the program loading to the RAM completed: 1st
Step Sl, step S2, step S6,
The process proceeds to step S7 and step S8. This time, since steps S3, S4, and S5 have been executed previously, the determination in step S8 is a match, and the RAM is
You can move on to executing the program.

FIG. 2 is a map of the memory 1 of an example of a microcomputer used in an embodiment of the present invention.

As is clear from FIG. 2, memory is expanded depending on the application program. As mentioned above, since the range to be sum checked is specified by the RAM program, there is no need to change the ROM program even if the size is changed in this way.

FIG. 3 shows the test memory 2 used in the embodiment of the present invention.
The details are as follows. From 4000H to 4002H, RA
M program start address storage area, 4 0
0 2 H to 4004H are RAM program size storage areas, and 4004H to 4006H are sum check value storage areas.

As shown in Figure 3, the start address of the RAM program and the size of the RAM program are set as multiples of 16, and each area is 2 bytes (4000H-400H).
4H). In addition to this agreement,
For example, the former is 2000H or less, the latter is 700H.
By setting rules such as 0H or more and OE000 or less and a multiple of 100H, the memory checking function can be made more robust.

Effects of the Invention As described above, the present invention provides a computer system that can execute a program in RAM without loading the program into RAM, and in which it is possible to reliably check whether or not the program in RAM is valid. can be taken as a thing. Also, even if the size of the RAM program changes, RO can be restored by simply changing a part of the RAM program.
You can deal with it without returning M.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing an embodiment of the program checking method of the present invention, FIG. 2 is a memory map diagram used in the embodiment, and FIG. 3 is a detailed diagram of the test memory used in the embodiment. FIG. 1...Memory map, 2...Memory for inspection.

Claims (1)

[Claims] If the ROM is equipped with a ROM, a RAM, and a test memory, and the program in the ROM reads a program from the outside into the RAM after power is turned on, the program in the RAM reads the program in the RAM after transferring control to the program in the RAM. The start address, size, and sum check value are stored in the test memory, and after the power is turned on, the R
If the OM program does not read a program from the outside into the RAM, the ROM program calculates the sum check value of the RAM program based on the start address and size of the RAM program in the test memory, and A program check method characterized in that the sum check value in a test memory is compared with a sum check value, and if they match, control is transferred to the program in the RAM, and if they do not match, an error is determined.