JP3060376U - Memory device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To prevent runaway of a program due to a malfunction of a memory. When a power-on reset signal generated in response to a power-on operation is supplied from an operation unit, a CPU (55) for every byte over the entire area of a RAM (3a).
₍₁₆₎ is written, and when this is completed, the value written in the RAM 3a is read byte by byte, and the read value is compared with the written value of 55 ₍₁₆₎ to determine whether or not the writing has been performed normally. Determine. When it is determined that writing has been performed normally, AA
₍₁₆₎ is written, and when this is completed, the value written in the RAM 3a is read byte by byte, and the read value is compared with the written AA ₍₁₆₎ to determine whether the writing was performed normally. Determine. When it is determined that the writing has been performed normally, the program 8 is started.

Description

[Detailed description of the invention]

[0001]

[Technical field to which the invention belongs]

 The present invention relates to a memory device that controls the execution of a program, and more particularly to a memory device that performs self-diagnosis of a memory prior to the activation of a system program and controls the execution of the system program based on the result of the self-diagnosis.

[0002]

[Prior art]

 Devices controlled by a program such as a computer or various other control devices are configured to perform a self-diagnosis or the like that the program is not damaged in an initialization process executed immediately after the power is turned on.

A central processing unit proposed in Japanese Patent Application Laid-Open No. 4-318628 is an example of the above-described device. When a microprogram is read from an external memory, a check generated according to a predetermined rule is performed. Sum data is added to the microprogram and stored in the CPU. In a check mode that is not executed during execution of the program, the microprogram stored in the CPU is read and the checksum data is stored in the CPU. It is an object of the present invention to reduce the memory capacity for storing a microprogram and to increase the execution speed by performing self-diagnosis of the damage of the microprogram by utilizing.

[0004] An apparatus controlled by a program includes a memory used for executing the program. Generally, immediately after the power is turned on, the value of the memory cell is undefined, that is, whether the value is 0 or 1 is not guaranteed. If a program is executed in such a state, an operation failure may occur. Therefore, in the above-described apparatus, prior to the execution of the program, specifically, the configuration is such that the values of all the memory cells are set to 0 (zero) by an initial setting process executed immediately after the power is turned on. It is.

A single-chip microcomputer and a test method thereof proposed in Japanese Patent Publication No. Hei 8-27730 are inventions characterized by a condition for clearing the value of a memory cell, and store secret information. For a single-chip computer, in response to a signal for setting a test mode provided as an operation mode for performing an operation test, an initialization routine for initializing, ie, clearing, information already stored is executed. The purpose of this is to achieve both the persistence of the test mode required for retesting after shipment and the security of confidential information that must not be read.

[0006]

[Problems to be solved by the invention]

 By the way, products that pass the operation test and are shipped may cause malfunctions due to improper handling after shipment or incompatibility of the operating environment. For example, in a memory, a short circuit (short circuit) between adjacent memory cells can be given. In some cases, the value of the memory cell is fixed to either 0 or 1 and the storage operation is impossible. Since a memory in which an operation failure has occurred cannot store a normal value at the location where the failure has occurred, using the memory for executing the program may cause the program to run away, that is, cause an abnormal operation. A runaway program could also cause damage to other parts of the equipment.

[0007] However, in the conventional device, no measure has been taken against a program runaway caused by a malfunction of the memory.

The present invention has been made in view of such circumstances, and performs a self-diagnosis of a memory prior to execution of a program, and rejects the execution of the program when the memory detects a malfunction. Accordingly, it is an object of the present invention to provide a memory device capable of preventing program runaway.

[0009]

[Means for Solving the Problems]

 The memory device according to the first invention is a memory device that controls the execution of a program in accordance with the state of the memory, and includes a memory, a program memory storing the program, and a plurality of predetermined predetermined values. Writing means for selecting one by one and writing the selected value to the memory each time, and reading the value written to the memory each time writing of the predetermined value to the memory is completed. Means for determining whether or not the read value matches the written predetermined value; and, when determining that the read value matches the written predetermined value, the program stored in the program memory is read. An execution control unit for executing the program when it is determined that the read value does not match the written predetermined value.

[0010] The memory device according to the second invention is characterized in that two values of 55 ₍₁₆₎ and AA ₍₁₆₎ are set in the writing means as predetermined values.

In the first and second inventions, regarding short-circuiting of adjacent memory cells, different values are written in two adjacent memory cells, respectively, and then the values written in each memory cell are read out. Detection is performed based on whether each read value matches the written value. In a situation where memory access is performed in byte units, it is possible to select a value with a different adjacent bit value, specifically 55 ₍₁₆₎ or AA _(16), as the value to be written for detection. desirable. For example, 55 ₍₁₆₎ becomes 01010101 ₍₂₎ when converted to a bit string, and AA ₍₁₆₎ becomes 10101010 ₍₂₎ .

In the storage operation of a memory cell, different values in a predetermined memory cell are separately written twice, and each time the writing is performed, the value written in the memory cell is read, and Diagnosis is made based on whether or not each read value matches the written value in each read process. For example, by writing 55 ₍₁₆₎ for the first time and writing AA ₍₁₆₎ for the second time, different values can be written for each bit position by performing the writing process twice. Note that the order of the predetermined values to be written by the writing process is the same as in the case of writing AA _{(16) the} first time and writing 55 _{(16) the} second time, contrary to the order described above.

Further, the values used for diagnosing the storage operation are not limited to two. Ie, divided three values in three degrees may be configured to write each in a given memory cell, in this case, for example, writes the 24 ₍₁₆₎ for the first time, the second time 49 _{(1 6 )} Is written for the third time, and 92 ₍₁₆₎ is written for the third time, and each time the value is written, the value written in the memory cell is read, and it is determined whether or not each read value matches the written value. Thereby, an equivalent effect can be obtained.

In these inventions, a self-diagnosis of a short and a storage operation of an adjacent memory cell of a memory is performed, and when a malfunction is detected, a program that may cause a runaway is not executed. Can be.

[0015]

[Embodiment of the invention]

 FIG. 1 is a block diagram showing a configuration of a memory device according to the present invention, and shows a printing apparatus as an example of the embodiment. In the figure, reference numeral 1 denotes a CPU for performing program control. The CPU 1 is connected via a bus 2 to a system memory 3 used for executing a program, a print control unit 4 for controlling a drive unit (not shown) such as a feed motor, and a buffer memory 5 for storing data to be printed. And a display section 6 for displaying the operation state of the apparatus, and an operation section 7 for receiving operations such as power-on and starting printing and generating a predetermined signal. The system memory 3 is composed of a RAM 3a and a ROM 3b, and a program 8 for control is stored in the ROM 3b. The CPU 1 reads out the program 8 from the ROM 3b and executes it using the RAM 3a, whereby the printing apparatus is program-controlled.

FIG. 2 is a flowchart showing a processing procedure relating to the execution control of the program 8. When receiving a power-on reset signal (Power On Reset: POR) generated in response to the power-on operation from the operation unit 7, the CPU 1 writes 55 ₍₁₆₎ for each byte over the entire area of the RAM 3a ( S1). When the writing is completed, the value written in the RAM 3a is read byte by byte, and the read value is compared with the written value 55 ₍₁₆₎ to determine whether or not the writing has been normally performed (S2). When it is determined that the writing has been normally performed, AA ₍₁₆₎ is written for each byte over the entire area of the RAM 3a (S3). When the writing is completed, the value written in the RAM 3a is read for each byte, and the read value is compared with the written AA ₍₁₆₎ to determine whether or not the writing has been normally performed (S4).

When it is determined that the writing has been performed normally, the power lamp indicating that the power of the display unit 6 is turned on is turned on (S5), and the program 8 is started. If it is determined in S2 that the writing of 55 ₍₁₆₎ has not been performed normally, or if it is determined in S4 that the writing of AA ₍₁₆₎ has not been performed normally, the program 8 is not started.

As described above, since the printing apparatus does not start the program in a situation where the program is expected to run out according to the result of the self-diagnosis of the memory, it is possible to prevent the program from running away. In addition, since the printing device turns on the power lamp when the self-diagnosis of the memory indicates that the operation is good, and does not turn on the power lamp when the operation is faulty, the user can use the power lamp. The malfunction of the memory can be detected based on the lighting state.

[0019]

[Effect of the invention]

 In some of the memory devices of the first and second inventions as described above, the memory is self-diagnosed prior to the execution of the program, and the program is not executed when the malfunction is detected. It is very effective in preventing runaway of the resulting program.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a memory device according to the present invention.

FIG. 2 is a flowchart illustrating a processing procedure related to execution control of a program.

[Explanation of symbols]

 1 CPU 3 system memory 3a RAM 3b ROM 8 programs

Claims (2)

[Utility model registration claims] 1. A memory device for controlling the execution of a program in accordance with the state of a memory, wherein a memory, a program memory storing a program, and a plurality of preset predetermined values are selected one by one. A writing means for writing the selected predetermined value to the memory each time; a means for reading the value written to the memory each time the writing of the predetermined value to the memory is completed; and a reading means for writing the read value. Means for determining whether or not the read value matches the predetermined value; and, when determining that the read value matches the written predetermined value, executing the program stored in the program memory and writing the read value. A memory device comprising: an execution control unit that does not execute the program when it is determined that the program does not match the predetermined value. 2. The writing means has a predetermined value of 55
2. The memory device according to claim 1, wherein two values of ₍₁₆₎ and AA ₍₁₆₎ are set.