JPH048822B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a deadman circuit that detects runaway of two CPUs, and more specifically relates to a deadman circuit that allows one deadman circuit to monitor runaway of two CPUs. .

[Conventional technology]

The conventional dead man circuit, as shown in Figure 3,
It was provided for each CPU (central processing unit). The purpose of using two CPUs in one device is to improve reliability, but the functionality of the entire device is ensured by the two CPUs. If any CPU stops functioning, the device itself stops functioning. Therefore, attaching a deadman circuit to each CPU is disadvantageous from the viewpoint of manufacturing costs, and it has been desired to monitor two CPUs with one deadman circuit.

[Problem to be solved]

This invention was made in view of the above circumstances, and aims to propose a deadman circuit that monitors two CPUs with one deadman circuit and can reset both CPUs at the same time if either one goes out of control. shall be.

However, since the entire device functions with two CPUs, determining which CPU is out of control and giving a reset signal only to that CPU would add unnecessary circuitry and diminish the significance of this invention. This is because you will have to do so.

[Means for solving problems]

That is, the deadman circuit for detecting the runaway of the two CPUs according to the present invention uses one of the deadman pulses of the same period output from the two CPUs as a trigger type flip-flop (hereinafter referred to as "T-F/F"). ), one output of this T-F/F is input to the D input terminal of a D-type flip-flop (hereinafter referred to as "D-F/F"), The other deadman pulse is inverted and inputted to the clock input terminal of the D-F/F, and the output of this D-F/F is input to one deadman circuit. It is characterized by resetting two CPUs.

[Effect]

According to the above configuration, the deadman pulses of the two CPUs are converted into one deadman pulse by the combination of one T-F/F and one D-F/F, and even if either CPU goes out of control, one deadman circuit operates and resets both CPUs.

〔Example〕

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

FIG. 1 shows an outline of the circuit, and reference numeral 1 in the figure is a deadman circuit according to the present invention. It consists of 5.

The output of the conventional deadman circuit 4 is the first CPU
6 and the reset ports of the second CPU 7. Furthermore, the input side of this deadman circuit 4 is connected as follows.

The deadman pulses of the first CPU 6 and the second CPU 7 have the same phase, the same frequency, and the same duty ratio, and the deadman pulse of the CPU 6 and the T-F/F2
Connect this T-F/F to the clock input terminal of
Connect the Q output terminal of No.2 to the D (data) terminal of D-F/F3. Next, the clock input terminal of DF/F3 is connected to the deadman port of CPU7 via inverter 5. And this D-
Q output terminal of F/F3 and conventional deadman circuit 4
is connected to the input terminal of

Furthermore, the T (trigger) input terminal and Q output terminal of T-F/F2 are connected.

When the phase of the deadman pulse of the CPU 7 is not inverted, the inverter 5 connects the rising edge of the input pulse to the clock input terminal of the D-F/F3 with the D-F/F/F3 clock input terminal.
This is necessary to avoid overlapping the rising edge of the D terminal input pulse of F3.

In the above configuration, the deadman circuit 1
It operates as shown in the figure. P1 in the diagram is CPU6
P2 is the deadman pulse of CPU7. B is the output pulse waveform of the Q output terminal of TF/F2, that is, the D terminal input pulse waveform of DF/F3. A is Q of D-F/F3
Output waveform of the output terminal, that is, deadman circuit 4
This is the input pulse waveform of

In Figure 2a, deadman pulses P1 and P2 are normal, so pulse waveforms B and A are pulses P1 and P2.
It has a regular waveform obtained by dividing 2 by 2. However, if the CPU 6 goes out of control as shown in c of the figure, suppose the deadman pulse P1 changes as shown in b of the figure. Then, as a result of the change in the output pulse waveform B, the input pulse waveform A of the deadman circuit 4 changes, so that the deadman circuit 4 applies a reset signal to both the CPU 6 and the CPU 7. The same thing happens even if the deadman pulse P2 changes in the same way.

Furthermore, if the deadman pulse P1 is no longer output due to the runaway of the CPU 6, the output pulse waveform B of the T-F/F2 remains at a low level, and the output of the D-F/F3 also remains low, as shown in c in the figure. Therefore, runaway can be detected by the conventional deadman circuit 4. The same applies when the deadman pulse P2 is no longer output.

〔effect〕

As described, according to this invention, T-F-F
Since it is sufficient to prepare one each of D-F/F and one simple phase inverter such as an inverter, it is advantageous in terms of manufacturing cost compared to attaching a dead man circuit to each CPU. be.

[Brief explanation of drawings]

FIG. 1 is a schematic circuit diagram showing an embodiment of the present invention;
FIG. 2 is a time chart for explaining its operation, and FIG. 3 is an explanatory diagram showing a conventional example. 1... Deadman circuit for detecting runaway of two CPUs, 2... T-F/F (trigger type flip-flop), 3... D-F/F (D type flip-flop), 4... ...Conventional dead man circuit, 5
...Inverter, 6,7...CPU.

Claims (1)

[Claims] 1 One of the deadman pulses of the same period output from the two CPUs is T-F/F.
input to the clock input terminal of , input one output of this T-F/F to the D input terminal of D-F/F,
The other deadman pulse is inverted and inputted to the clock input terminal of the D-F/F, and the output of this D-F/F is input to one deadman circuit. Horn
A deadman circuit for detecting runaway of two CPUs, characterized in that it resets the CPUs.