JPS63282858A - System for preventing program runaway - Google Patents

Abstract

PURPOSE:To prevent a microprogram from generating runaway by interrupting a microprocessor at a fixed period, reading out the state of a processing flag from processing flag register to detect whether respective processing is successively executed or not, and executing prescribed abnormality processing when the processing is not successively executed. CONSTITUTION:A processing flag is inverted every end of each processing out of processing #1, #2 and the processing flags '1', '0' are alternately changed at the time of executing the microprogram. The processing flag can be decided by checking that the contents of a register 5 storing the processing flag is alternately changed to '1' and '0' every external periodical interruption, i.e. every time when the output of a counter 2 is inputted to an INT terminal of the microprocessor 1 as an interruption. Consequently, highly reliable runaway prevention can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for preventing program runaway in processing operations of a microprocessor.

[Prior Art] FIGS. 3 and 4 show a flowchart of a microprogram showing a conventional runaway prevention method and a block diagram for realizing this.

In Figure 4, (1) is a microprocessor, (3)
is a decoder, (4) is a sequence counter with a pair of reset terminals, and the output of the counter is a non-maskable interrupt (hereinafter referred to as NMI) of the microprocessor (1).

: Non-Maskarable Interrupt
t) connected to the terminal.

Next, the operation will be explained. Microprocessor (1)
The processing order of the operation is defined by the microprogram, and starts from 5TART as shown in FIG.
5 TEP is executed according to the order of its microprograms. The part indicated by rOut XXX J in this microprogram is for performing a reset processing operation in which a counter reset output is generated from the decoder (3) in FIG. XXX,”~rol]T XX
For example, the processing time between
By creating a microprogram that completes within 7-116.2ms, the counter in Figure 4 (
The output of 4) is not always output under normal conditions, and no NMI occurs in the microprocessor (1).

The occurrence of various types of noise such as lightning or lightning may cause the microprocessor (1) to temporarily malfunction, resulting in an abnormal state (runaway state) in the processing of the microprogram. In such a case, correct processing may not be performed and the reset processing operation rOUT XXX J itself may not be performed, or the above reset processing operation amount, that is,
The processing time between XX J and rOUT XXX J often exceeds the predetermined time = 116.2 ms. Therefore, the output of the decoder (3) does not come out within the counter time of the counter (4), and the output of the counter (4) comes out, causing an NMI to the microprocessor (1). That is, runaway is detected and the NM shown in FIG.
If you handle the abnormality when I occurs (for example, 5 of the program
(Return to TART and start over from the beginning, etc.) can prevent runaway.

In addition, this type of runaway prevention method is generally referred to as “watch”.
This is called the dog timer method.

[Problems to be Solved by the Invention] Since the conventional runaway prevention method is configured as described above, the reset processing operation r OUT XXX J microprogram instruction and reset processing operation amount, that is, r
If the time between OUT XXX J and rOUT XXX J runs out of control while being in the correct state, for example, if the runaway occurs in an endless loop as shown in FIG. 5, there is a problem that the runaway cannot be prevented.

This invention was made to solve the above-mentioned problems, and even when a certain part of the microprogram causes an endless loop (runaway) due to the occurrence of noise such as lightning, it can detect the runaway. The purpose of this invention is to obtain a highly reliable program runaway prevention method that can prevent runaways.

[Means for Solving the Problems] The program runaway prevention method according to the present invention includes a processing flag in which 1 and O are alternately inverted each time each processing by a microprocessor is completed, It detects whether or not each process is being performed sequentially by interrupting the process at regular intervals and reading the status of this process flag from the process flag register. , which is characterized by preventing runaway of microprograms.

[Operations] In this invention, the processing flags of the microprogram are alternately inverted by 170, so that each even 3
! ! It is confirmed that (processing 1tl, #2) has passed reliably, and runaway can be detected.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
The figure shows a flowchart of the microprogram of the present invention, and FIG. 2 is a circuit configuration diagram including a microprocessor for executing this microprogram, where (1) is the microprocessor and (2) is the The sequence counter (5) changes to 1 and O every time each process ends.
indicates a processing flag register that stores processing flags that are alternately inverted.By interrupting the microprocessor at regular intervals and reading the state of the processing flags, it is possible to detect whether each process is being performed sequentially. It is done like this.

The operation of the above configuration will be explained.

The normal operation of the microprogram in Figure 1 is 5TA.
At RT (start), first initialize to initialize the state, reset the processing flag, and then proceed to processing #l and processing #2! Continue filling in A until 5TOP is specified. and,
The processing flag is inverted every time the processing #1 and processing #2 are completed, so that the processing flag 170 is alternately changed during execution of the microprogram.

The processing flag is determined every time there is a regular interrupt from the outside (when the output of the counter (2) in Figure 2 is generated as an interrupt at the INT terminal of the microprocessor (1)). A register that stores (
By confirming that the contents of 5) are 170 alternating.

On the other hand, if various types of noise such as lightning occur and the operation of the microprocessor (1) in FIG. 2 temporarily malfunctions, and the microprogram processing becomes abnormal (runaway state), processing #1 in FIG. The process may hang in the middle, jump to process #1 from the middle of process #2, or become unsure of what to do.

Even in such cases, interrupts occur at regular intervals, and an abnormality can be detected by checking the processing flag and confirming that the contents of the register (5) that stores it are I10 alternating. The state can be restored in the shortest possible time.

Note that in the above embodiment, two cases, Process #1 and Process #2, were explained, but in a case where there are more processes, or when a process flag is provided for each of multiple processes such as Process #1 and Process #2. A similar method can be applied to .

[Effects of the Invention] As described above, according to the present invention, the processing flag is alternately changed 170 times for each process of the microprogram, and the processing flag is changed by periodically inputting a signal to the interrupt input of the microprocessor. Since this check is performed, highly reliable runaway prevention can be performed.

[Brief explanation of drawings]

FIG. 1 is a flowchart of a runaway prevention microprogram according to an embodiment of the present invention, FIG. 2 is a block diagram for executing this runaway prevention microprogram, and FIGS. 3 and 4 explain a conventional runaway prevention method. FIG. 5 is an explanatory diagram showing a runaway state in an endless loop in a conventional example. In the figure, (1) is a microprocessor, (2) is a sequence counter, and (5) is a processing flag register. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1 and 0 each time the microprocessor completes each process.
The microprocessor is provided with processing flags that are alternately inverted, and by interrupting the microprocessor at regular intervals and reading the state of the processing flags from the processing flag register, it can be determined whether each processing is being performed sequentially. A program runaway prevention method is characterized in that it detects and performs predetermined abnormality processing when executions are not performed in sequence to prevent runaway of a microprogram.