Malfunction preventing system for a microcomputer system

• US 4,363,092 A
• Filed: 09/12/1979
• Issued: 12/07/1982
• Est. Priority Date: 10/25/1978
• Status: Expired due to Term

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Hosaka, Akio, Abo, Toshimi
• Primary Examiner(s): Springborn, Harvey E.
• Application Number:
  US06/075,183
• Time in Patent Office: 1,182 Days
• Field of Search: 364/431, 364/200 MS File, 364/900 MS File, 123/478
• US Class Current: 714/23
• CPC Class Codes: F02D 41/263 the program execution being modifiable by physical parameters
• CPC Class Codes: F02D 41/266 the computer being backed-up or assisted by another circuit, e.g. analogue
• CPC Class Codes: G06F 11/0757 by exceeding a time limit, i.e. time-out, e.g. watchdogs

Abstract

A malfunction preventing system for a microcomputer system is disclosed which detects an abnormal condition in the program execution to produce an alarm or reset signal to automatically restart the computer. The malfunction preventing system is applicable to automotive engine control wherein the computer is capable of returning to normal operation upon detecting a malfunction in program operation for fuel parameter calculation, thereby to keep the automotive engine control in order.

Claims

1. Apparatus for preventing certain malfunctions of a microcomputer that is normally periodically cycled through a program, the microcomputer including a reset and initialization input terminal, the apparatus comprising a reset circuit for normally applying a first voltage to the reset and initialization input terminal, the microcomputer responding to the first voltage at the reset and initialization input terminal to continuously recycle the program, means responsive to power being initially applied to the microcomputer and the reset circuit for activating the reset circuit so the reset circuit applies a second voltage to the reset input for a predetermined interval after power is initially applied to the microcomputer and reset circuit, the microcomputer responding to the second voltage to reset the program to a starting point and initialize parameters associated with the program, the predetermined interval being greater than a predetermined time required for the microcomputer to execute a program cycle plus the time required to reset and initialize the microcomputer, the microcomputer deriving a program run impulse in response to the microcomputer executing each program cycle, whereby the microcomputer while normally operating derives adjacent periodic program run impulses at intervals spaced from each other by a predetermined time, the predetermined time being less than the predetermined interval, and means connected to the microcomputer to be responsive to the program run impulses for supplying the second voltage to the reset and initialization input terminal in response to a pair of the impulses not occurring in a predetermined duration, the predetermined duration being greater than the predetermined time, whereby the program is immediately reset and initialized in response to the microcomputer not executing the program within the predetermined duration.

2. In combination,

a microcomputer for normally periodically executing a program, said microcomputer including an output means for generating an output signal in response to the microcomputer executing the program, the output signal having a predetermined periodically occurring characteristic only while the microcomputer normally periodically executes the program;

apparatus for preventing certain malfunctions of the microcomputer,

said apparatus comprising;

first means connected to the output means to respond to said output signal for indicating an abnormal condition of the microcomputer in response to the predetermined periodic characteristic not occurring for a time interval in excess of a predetermined interval greater than the period of the predetermined periodic characteristic;

second means connected to the first means to respond to the abnormal condition being indicated for periodically resetting the program while the abnormal condition is indicated by the first means; and

third means connected to respond to the second means for deriving an alarm signal in response to the program being repeatedly reset by the second means at a frequency exceeding a predetermined occurrence frequency.

4. The combination of claim 2 or 3, wherein said first means comprises:

a capacitor, means for charging the capacitor with a predetermined time constant between adjacent occurrences of the output signal, means for discharging the capacitor in response to said output signal, and means for sensing the voltage across the capacitor for indicating the microcomputer abnormal condition in response to the voltage across the capacitor exceeding a predetermined level associated with;

(a) the time constant, (b) a charging voltage for the capacitor and (c) the time between adjacent occurrences of the output signal.

5. The combination of claim 2 or 3 wherein a portion of the program includes a routine that is cyclically executed in response to the microcomputer normally periodically executing the program, said routine commanding said output means of said microcomputer to derive a pulse signal, said pulse signal being said output signal with the predetermined periodic characteristic.

7. The combination of claim 2 or 3, wherein said microcomputer includes a memory, and means for deriving a read/write signal for controlling the memory, said pulse signal being a read/write signal of the microcomputer.

8. The combination of claim 2 or 3, wherein said first means comprises a retriggerable monostable multivibrator.

9. The combination of claim 2 or 3 wherein said microcomputer includes a reset input and said second means includes means responsive to the indication of abnormality for deriving a reset signal that is coupled to the reset input of the microcomputer system.

10. The combination of claim 9 further including a real time device, the microcomputer including an output port for supplying a control signal to the real time device.

13. The combination of claim 2, 3 or 4, wherein said program includes instructions for controlling fuel supply for an automotive engine based on operating parameters for a controller of the automotive engine.

3. In combination,

a microcomputer, said microcomputer including an output means for detecting a normal operating condition of the microcomputer, said output means normally producing an output signal with a predetermined periodic characteristic while the microcomputer operates in the normal condition and discontinuing derivation of said output signal in response to the microcomputer failing to operate in the normal condition,

apparatus for preventing certain malfunctions of the microcomputer, said apparatus comprising:

first means connected to said output means for detecting said output signal of said output means and for indicating a failure of the normal microcomputer operation in response to said output signal not being derived by the output means and detected by the first means for a time interval longer than the time between adjacent occurrences of the predetermined periodic characteristic of said output,

second means responsive for periodically resetting the microcomputer to an operating point in the normal operating condition in response to the first means indicating the failure,

third means for counting occurrence of said second means resetting the microcomputer to derive a counted value signal, means for comparing a value indicated by the counted value signal with a predetermined value for producing an alarm signal in response to the value associated with the counted value being larger than said predetermined value; and

a warning system responsive to the alarm signal for deriving an indication of failure of normal operation of the microcomputer.

6. The combination of claim 3, wherein said program includes an interrupt routine, said microcomputer deriving said pulse signal after confirming execution of the interrupt routine.

11. In combination,

a microcomputer including means for deriving a program run signal in response to each execution of a normally periodically recurring program of the microcomputer;

apparatus for preventing certain malfunctions of the microcomputer, said apparatus comprising;

first means responsive to the program run signal for indicating that the program run signal is not being derived for a predetermined time interval in excess of the period between adjacent occurrences of the program run signal while the program normally recurs, said first means including;

a capacitor, means for charging the capacitor with a predetermined time constant between adjacent occurrences of the program run signal, means for discharging the capacitor in response to said program run signal, and means for sensing the voltage across the capacitor for deriving said indication in response to the voltage across the capacitor exceeding a predetermined level associated with;

(1) the time constant, (2) a charging voltage for the capacitor, and (3) the time between program run signals while the program normally recurs;

second means responsive to said first means for periodically resetting the microcomputer program to a starting point while the indication is being derived;

12. third means responsive to the second means for counting the number of times the second means resets the computer;

and

means responsive to the third means for deriving an alarm signal in response to the counted value being above a predetermined value.