JPS622683Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fault diagnosis circuit for a microcomputer that can diagnose a fault without providing a special output port for sending diagnostic pulses to the microcomputer.

In recent years, the use of microcomputers has rapidly progressed, and there is a tendency for various electronic devices to be driven and controlled by a plurality of microcomputers. in this case,
If a microcomputer itself breaks down, there is a risk of a serious accident. Therefore, multiple microcomputers mutually diagnose faults to form a fault diagnosis circuit, and if a fault is detected, the control system is activated. By forcing control to the safe side, a fail-safe system is constructed, greatly improving safety.

FIG. 1 is a circuit diagram showing an example of a fault diagnosis circuit for a microcomputer based on mutual diagnosis, which has been commonly used in the past. In this case, the two microcomputers 1 and 2 output various control outputs via data buses DB ₁ and DB ₂ to output ports.
The latch pulses L ₁ and L ₂ output from P ₁₀ and P ₂₀ are taken into the latch circuits 3 and 4 and outputted, thereby controlling each control section. On the other hand, the microcomputers 1 and 2 have output ports P ₁₁ ,
From _P23 , diagnostic pulses A and B with a constant period T shown in FIG. 2 are sent out. The microcomputers 1 and 2 each receive the diagnostic pulses B and A generated by the other at input ports.
Monitoring is performed by taking in via P ₁₂ and P ₂₂ and sampling with period T of square wave diagnostic pulses A and B. That is, if the microcomputers 1 and 2 on the other side are operating normally, the sampling outputs of the diagnostic pulses A and B should always alternate between "H" and "L". On the other hand, if the microcomputers 1 and 2 run out of control or enter a closed loop or other malfunction, the cycles of the diagnostic pulses A and B sent from the microcomputers may be disrupted, or This results in the output being fixed at either the "H" or "L" level. Therefore, the other microcomputer sequentially samples the diagnostic pulses different from the normal one, and
Fail-safe control is performed by detecting a failure when the deviation from the normal state exceeds a standard value.

However, in the above-mentioned configuration, the output port is only used to output a fixed period rectangular wave as a diagnostic pulse to each microcomputer 1, 2.
Requires P ₁₁ and P ₂₃ . In this case, the microcomputer makes effective use of its limited output ports, and it is extremely disadvantageous for one output port to be used exclusively for sending out diagnostic pulses, and this output port cannot be used for anything else. In other words, the functionality of microcomputers can be greatly improved.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a fault diagnosis circuit for a microcomputer that does not require an output port for transmitting diagnostic pulses to the microcomputer.

To achieve this purpose, the present invention uses another output port signal, such as a latch pulse, which is output at least once for one loop control, to trigger a flip-flop circuit, and the output of this flip-flop circuit is used as a diagnostic pulse to trigger the other output port signal. This is used to supply the diagnostic pulse input port of the microcomputer. Hereinafter, the microcomputer failure diagnosis circuit according to the present invention will be explained in detail with reference to the drawings.

FIG. 3 is a circuit diagram showing an embodiment of the microcomputer failure diagnosis circuit according to the present invention, and the same parts as in FIG. 1 are denoted by the same symbols and detailed explanation thereof is omitted. In the figure, numerals 5 and 6 are T-type flip-flops, and these flip-flops 5 and 6 are used for the fourth output from the output ports P ₁₀ and P ₂₀ of the microcomputers 1 and 2 for each loop control.
Latch pulses L ₁ and L ₂ of period T shown in Figure a are input as a trigger. Therefore, the output terminals Q of the flip-flops 5 and 6 output a rectangular wave that is inverted to "H" and "L" at every cycle T, as shown in FIG. 4b. The output signals of the flip-flops 5 and 6 are connected to the diagnostic pulse input terminals P ₁₂ and P ₂₂ of the opposing microcomputers 2 and 1, respectively.
are supplied respectively.

Therefore, in the fault diagnosis circuit for the microcomputer configured in this way, the flip-flops 5 and 6 are activated every time the latch pulses L ₁ and L ₂ of period T are output for each loop control of the microcomputer. will be triggered, and each time it is triggered, it will be inverted and the diagnostic pulses A and B shown in FIG. 4b will be sent out. This diagnostic pulse A, B
are supplied to the microcomputers 2 and 1 on the opposite side from the microcomputers that received the trigger latch pulses L ₁ and L ₂ , respectively. The microcomputers 1 and 2 sample and take in the diagnostic pulses B and A supplied from the flip-flops 6 and 5 at every cycle T via diagnostic pulse input terminals P ₁₂ and P ₂₂ , respectively. In this case, if the microcomputers 1 and 2 are operating normally, the latch pulses L ₁ and L ₂ are sequentially sent out at a period T, respectively. Therefore, flip-flops 5, 6
is always triggered every time the latch pulses L ₁ and L ₂ are generated, and the diagnostic pulses A and B, which are inverted to "H" and "L" at every time T, are sent out. On the other hand, the other microcomputers 2 and 1
Diagnostic pulses A and B are sampled sequentially at period T timing. As a result, diagnostic pulse A,
The sampling output of B is always “H” if the other party’s microcomputer is operating normally.
“L” will be repeated. On the other hand, if the microcomputers 1 and 2 malfunction for some reason, such as the program running out of control or entering a closed loop, the generation cycle of the latch pulses L ₁ and L _{2 may be disrupted, or the latching pulses L 1 and L 2} may become "H" or " It will stop in the "L" state. When the latch pulses L ₁ and L ₂ exhibit an abnormal state in this way, the operation of the flip-flops 5 and 6 is also disturbed, and as a result, the diagnostic pulses A,
B will also be disrupted. In this way,
If a disturbance occurs in the diagnostic pulses A and B, the sampling outputs of the microcomputers 1 and 2 that sample the diagnostic pulses A and B of the other party will no longer become "H" and "L" in sequence. If the sampling output of diagnostic pulses B and A deviates from the normal state by more than a predetermined reference value, the microcomputers 1 and 2 detect a failure in the other microcomputer. As such, it not only sends out a failure detection signal, but also performs fail-safe control in the event of a failure.

Therefore, in such a configuration, since the latch pulses L ₁ and L ₂ are used to generate diagnostic pulses, the microcomputers 1 and 2 do not need output ports for transmitting diagnostic pulses, which were required in the past. become. Therefore, among the limited ports, the microcomputers 1 and 2 can effectively utilize the output ports for transmitting diagnostic pulses that are no longer needed, thereby significantly improving their functionality. In this case, two flip-flop elements are required, but this is much more advantageous than the fact that one output port of the microcomputer can be effectively used.

In the above embodiment, only the case where the latch pulse is used to trigger the flip-flop for generating the diagnostic pulse is explained, but the present invention is not limited to this, and the present invention is not limited to this. It goes without saying that any signal may be used as long as it is generated once.

As explained above, the present invention provides a fault diagnosis circuit for a microcomputer that detects a fault by mutually monitoring diagnostic pulses of a fixed period supplied from each other. Another output port signal generated twice is used to trigger a flip-flop, and the flip-flop output is supplied as a diagnostic pulse to the other microcomputer. Therefore, the microcomputer has the advantage that the output ports used only for sending out diagnostic pulses are no longer needed, and these output ports can be effectively used for other functions.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a conventional fault diagnosis circuit for a microcomputer, Fig. 2 is an operating waveform diagram of Fig. 1, and Fig. 3 is a circuit diagram showing an embodiment of a fault diagnosis circuit for a microcomputer according to the present invention. , FIGS. 4a and 4b are operation waveform diagrams of each part of FIG. 3. 1, 2... microcomputer, 5, 6...
Flip flop.

Claims (1)

[Scope of utility model registration request] The first and second microcomputers are each triggered using another control output signal output from the first and second microcomputers at least once for one loop control, and the output thereof is used as a trigger signal. a flip-flop that supplies diagnostic pulses to the microcomputer on the side that does not receive the supply; the first and second microcomputers mutually diagnose failures by detecting an abnormality in the diagnostic pulses.