Electrical Device With Input and Output Ports for Changing the Multiplex Number of Transmittal Buses and System Using the Electrical Device

1. Field of the Invention

The present invention relates to an electrical device securing the normality of its output signals, particularly to such a system using the electrical device suitable for composing an input and output terminal or a transmittal terminal of a high reliability system as a fault tolerant system.

2. Description of the Related Art

The first conventional method for constructing a fail safe system is popularly realized by detecting faults in an electrical device or an electrical circuit adapting a self-checking methodology and realizing continuous operations of the fail safe system by changing the configuration of the system based on the fault detecting results.

Examples of such an approach are disclosed in the following references.

(1) "A 32-bit Fail Safe MPU Board" by Masayuki Umeyama,

Japan Signal Technique Report, Vol. 16, No. 3, pp. 11-16 (1992)

(2) "Development of A 32-bit Fail Safe CPU" by Noboru Asano, Traffic Electronics and Rail Way Research Committee Report of The Institute of Electrical Engineer of Japan, TER-92-35, pp. 31-41 (1992).

The disclosed methods for realizing a fail safe function detect faults in circuits by using a duplicated circuit such as a memory or a micro-processor and collating signals on buses connected to the duplicated circuit.

Then, as in the second reference, a method of feeding back output signals and collating the output signals and signals to be output, is popularly used to secure the normality of the output signals.

The above-mentioned conventional techniques disclosed in the Japan Signal Technique Report and the Traffic Electronics and Rail Way Research Committee Report of The Institute of Electrical Engineer of Japan, are effectual in the points that those techniques can be easily realized by using general purpose micro-processors or memories. However, the convenience of connection with an outer circuit is not much regarded in the techniques. In the above-mentioned techniques, it is required to use a duplex circuit as a circuit to be connected to a self-checking circuit. However, although a circuit synchronizing with a processor, such as a memory, can be simply duplicated and dealt with logically as a simple circuit, such a circuit operating asynchronously with a processor as a transmission interface connected with an outer circuit disturbs the synchronization of a whole system, only by simply duplicating the circuit. Then, as for such a circuit, it is desirable to provide two logically different circuits or devices, but it is not always necessary to connect such a circuit to an outer duplex bus as shown FIG. 7. And many of conventional transmission interfaces are designed so as to be connected to a non duplex bus (hereinafter called as a simplex bus) and can not be connected to a duplex bus as shown FIG. 7. Then, since error correcting detection of output signals is possible if error correcting codes are added to signals output to a bus, duplication of an outer bus is not always necessary.

The conventional output collating method of feeding back output signals is an excellent one for securing the normality of output signals. And, particularly, the method can detects a fault such as disconnection of a wire, a contact failure, etc., as to output signals of a circuit on a wired board, and a fault such as an inferior wire-bonding, an inferior soldering of a pin (or a lead), etc., as to a circuit in a semiconductor package. However, in the method, a counter-measure to increasing of the required points of contact or terminals of pins (or leads) is not much regarded yet. Then, the same number of terminals for the feedback as that for output signals is needed for feeding back the output signals. For example, totally terminals are necessary in the method for an address signal of 32 bits and a data signal of 32 bits. Further, if an outer bus is duplicated as mentioned above, 256 terminals are necessary. Especially, in such a system, an increasing of terminals in a semiconductor device causes an increase of a chip size or a package size which causes in its turn an increase of a failure rate besides weight and volume of a device.

Further, since a use of an electrical device having a self-checking function is restricted to a special field and the mass production effects are not large, a cost of a device becomes very high if design and production is individually done for each device for adapting the device to a simplex bus or a duplex bus.

The present invention offers an electrical device or a system using the electrical device, capable of corresponding to both a simplex bus and a multiplex bus.

Additionally, the invention offers an electrical device capable of corresponding to both buses of a simplex bus and a multiplex bus or a fault tolerant system using the electrical device, capable of securing the normality of output signals without increasing of the terminal number.

One of features of the present invention is that an electrical device according to the present invention has such input and output parts in a number corresponding to the number of buses connected to the input and output ports, that the same signals are output from the input and output ports to the multiplex bus if the input and output ports are connected to a multiplex bus. And if the input and output ports are connected to a simplex bus, at least one pair of the input output ports are connected each other, and a signal is output from one of the input and output ports, and the output signal is collated with the signal to be output, by feeding back the output signal from another one of the input and output ports, when outputting signals.

Another one of features of the present invention is that an electrical device according to the present invention has such two input and output ports connected to buses having the same specification that the same signals are output from the two input and output ports if the input and output ports are connected to a duplex bus, and if the two input and output ports are connected to a simplex bus, the terminals of the two input and output ports are connected each other, a signal is output from one of the input and output ports and the output signal is collated with the signal to be output, by feeding back the output signal from another one of the two the input and output ports, when outputting signals.

By the above-mentioned features, if the input and output parts are connected to a duplex bus or a multiplex bus, the signals output on the buses are collated and the normality of signals output from the input and output port are secured by confirming the agreement among the collated signals.

Further, if the input and output port are connected to a simplex bus, the normality of signal output from the input and output part is secured by feeding back an output signal and collating the output signal with the fed back output signal.

Furthermore, since another one of the input and output ports connected to a duplex bus, except one of the input and output ports being used to output signals to the bus, is used for the signal feedback, it is possible to feed back the output signals without increasing the number of terminals in the input and output ports.

FIG. 1 is a diagram showing a fundamental embodiment of the present invention for the duplex bus connection mode.

FIG. 2 is a diagram showing a fundamental embodiment of the present invention for the simplex bus connection mode.

FIG. 3 shows the constitution of an interface part for the duplex bus connection mode.

FIG. 4 shows the constitution of an interface part for the simplex bus connection mode.

FIG. 5 shows an example of a way of correcting comparators.

FIG. 6 shows another example of a connection way of comparators.

FIG. 7 is a diagram showing the constitution of an example of a self-checking system to which the embodiment of the present invention is applied.

FIG. 8 is a diagram showing the constitution of another example of a self-checking system to which the embodiment of the present invention is applied.

FIG. 9 is a diagram showing the constitution of an example of a continuous operation type fault tolerant system to which the embodiment of the present invention is applied.

FIG. 10 is a diagram showing the constitution of another example of a continuous operation type fault tolerant system to which the embodiment of the present invention is applied.

Hereinafter, embodiments of the present invention are explained reference to drawings.

In FIGS. 1 and 2, the fundamental concept of the present invention is shown. FIG. 1 shows an electrical device 10 according to an embodiment of the present invention, which, for example, is connected to two buses 150 and 160 in an outer duplex bus and includes duplicated electrical circuits (CPU, I/O(input and output terminal), etc.) 11 and 12. Outputs of the electrical circuits 11 and 12 are connected to the buses 150 and 160 via input and output terminals 15 and 16, respectively. The two outputs of the electrical circuits 11 and 12 are collated by a comparator 14, and the comparator 14 detects a fault occurring in one of the two electrical circuits 11 and 12 as the disagreement between the two outputs and provides external the fault indication of occurrence.

FIG. 2 shows an electrical device 10 of another embodiment of the present invention, in which input and output terminals 15 and 16 are connected to a bus 150 in an outer simplex bus, an internal switch of 13 the electrical device 10 being opened in outputting signals to the bus 150 and closed in inputting signals from the bus 150. By the embodiment, the signals output to the bus 150 are fed back via the input and output terminal 16 and collated with the signal to be output at the output of the electrical circuit 11 by the comparator 14. Then, by the collating results of the comparator 14 it is assured that signals are normally output from the input and output terminal 15 to the bus 150.

FIGS. 3 and 4 are diagrams showing composition of an interface part with the outer buses, in an embodiment according to the present invention. FIG. 3 is a diagram of an example showing the composition in which the electrical device 10 is connected to the buses 150 and 160 of the outer duplex bus and a mode switching signal 166 is set to H level. The output signal 153 of the electrical circuit 11 is output to the bus 150 from a tri-state buffer 151 via the input and output terminal 15. The tri-state buffer 151 is controlled by an input and output control signal 154. The input and output control signal 154 from the electrical circuit 11 is set to H level and the state of the tri-state buffer 151 becomes enabled, in outputting signals. In inputting signals, the input and output control signal 154 is set to L level and the state of the tri-state buffer 151 become disabled, namely, a high impedance state. Then, the electrical circuit 11 can take in signals on the bus 150 by using a signal line 155 via an input buffer 152.

The output signal 163 from the electrical circuit 12 is output from a tri-state buffer 161 to the bus 160 via the input and output terminal 16. The tri-state buffer 161 is controlled by an input and output control signal 164 as explained below. In outputting signals, an output 168 of an AND gate 167 becomes H level state since the input and output control signal 164 from the electrical circuit 12 is set to H level and a mode switching signal 166 is set to H level, and then the state of the tri-state buffer 161 becomes enabled. In inputting signals, the output 168 of the AND gate 167 becomes L level state since the input and output control signal 164 is set to L level, and then the state of the tri-state buffer 161 becomes disabled, namely, a high impedance state. Then, the electrical circuit 12 can take in signals on the bus 160 by using a signal line 165 via an input buffer 162.

By the embodiment, in outputting signals, the comparator 14 can monitor operations of the electrical circuits 11 and 12 by collating the signals output from the tri-state buffers 152 and 162 via the input buffers 152 and 162. And, in inputting signals, operations of an outside electrical device outputting signals to the buses 150 and 160 can be monitored by collating the signals on the buses 150 and 160.

FIG. 4 is a diagram showing an example in which the electrical device 10 is connected to an outer simplex bus 150. In the case, this mode switching signal 166 is set to L level. The electrical circuit 11 can transmit signals with the outer simplex bus 150. And the output 168 of the AND gate 167 always becomes a L level state since the mode switching signal 166 is set to L level, and then the state of the tri-state buffer 161 always is disabled, namely, a high impedance state. Therefore, the input and output terminal 16 is used exclusively for inputting signals. In outputting signals, signals output from the input and output terminal 15 to the bus 150 appear as the output 165 of the input buffer 162. In inputting signals, signals input to the bus 150 appear as the output 165 of the input buffer 162. Then, the electrical circuit 12 can take in signals on the bus 150 by using a signal line 165 via an input buffer 162.

By the embodiment, the comparator 14 can assure that signals from the electrical circuit are normally output to the bus 150, by collating the outputs of the tri-state buffer 151 with the signals output on the bus 150, in outputting signals. And, in inputting signals, operations of an outside electrical device outputting signals to the buses 150 and 160 can be monitored by collating the signals on the buses 150 and 160.

In an example shown by FIG. 4, only the collation by the feedback of the signal output on the bus 150 in outputting signals is explained for simple explanation. However, it is more desirable to make it possible that operations of the electrical circuits 11 and 12 are monitored besides the collation by the feedback of the signal output on the bus 150, by increasing the number of comparators. Examples of increasing of comparators are shown in FIGS. 5 and 6.

FIG. 5 shows an embodiment in which the comparator 14 is inserted between the signal lines 155 and 165, and a comparator 141 between the signal lines 163 and 165. In the duplex bus connection mode of the embodiment, the comparator 14 monitors operations of the electrical circuits 11 and 12 in outputting signals, and operations of an outside electrical device outputting signals to the buses 150 and 160 by collating the signals on the buses 150 and 160 in inputting signals.

And, in the simplex bus connection mode, the comparator 14 assures that signals from the electrical circuit are normally output to the bus 150, by collating the outputs of the tri-state buffer 151 with the signals output on the bus 150, and then the comparator 141 monitors operations of the electrical circuits 11 and 12 by collating the signals 165 output on the bus 150 from the electrical circuit 11 with the output signals from the electrical circuit 12, in outputting signals. And the comparator 14 monitors operations of an outside electrical device outputting signals to the buses 150 and 160 by collating the signals on the buses 150 and 160 in inputting signals.

FIG. 6 shows an embodiment in which the comparator 141 is inserted between the signal lines 153 and 163, and a comparator 14 is inserted between the signal lines 155 and 165. In the duplex bus connection mode of the embodiment, the comparators 141 and 14 monitor operations of the electrical circuits 11 and 12 in outputting signals, and operations of an outside electrical device outputting signals to the buses 150 and 160 by collating the signals on the buses 150 and 160 in inputting signals.

And, in the simplex bus connection mode, the comparator 14 assures that signals from the electrical circuit are normally output to the bus 150, by collating the outputs of the tri-state buffer 151 with the signals 165 output on the bus 150, and then the comparator 141 monitors operations of the electrical circuits 11 and 12 by collating the signals 153 from the electrical circuit 11 with the output signals 163 from the electrical circuit 12, in outputting signals. And the comparator 14 monitors operations of an outside electrical device outputting signals to the buses 150 and 160 by collating the signals on the buses 150 and 160 in inputting signals.

Although there exist other applicable ways of connecting comparators besides the examples shown in FIGS. 3 to 6, such comparators all operate in the same ways as mentioned above.

FIGS. 7 and 8 show examples of self-checking systems using the electrical device 10 of the above-mentioned embodiment by the present invention.

If the electrical device 10 of the above-mentioned embodiment is connected to the buses 150 and 160 of an outer duplex bus, the electrical device 10 is used by in the duplex bus connection mode, that is, the mode switching signal 166 is set to H level, as shown by FIG. 3. In the embodiment, memories 159 and 169 are connected to the buses 150 and 160, respectively, and the both systems operate synchronously. An I/O interface 17 such as a transmittal interface with outside devices is connected to the buses 150 and 160.

If the electrical device 10 of the above-mentioned embodiment is connected to a simplex bus 150, the electrical device 10 is used in the simplex bus connection mode, that is, the mode switching signal 166 is set to L level, as shown by FIG. 4.

FIGS. 9 and 10 show embodiments of a continuous operation system which is accomplished by developing each of the embodiments shown by FIGS. 7 and 8. The final output 19 is gained by switching the outputs of the I/O devices shown FIGS. in 7 and 8 by an output selecting mechanism 18. The output selecting mechanism 18 selects the signal regarded as normal based on error detecting signals output from the comparators 14 and 141 in the electrical device 10.

By the embodiment, a continuous operation system making the most of the feature of securing the normality of output signals from the electrical device 10, can be realized. Furthermore, it is possible to realize a more reliable system by further multiplying the output selecting mechanism.

As mentioned above, by the embodiment, it is not necessary to develop individually the electrical device 10 for each of the simplex bus and the duplex bus since the same electrical device 10 can correspond to both the simplex bus and the duplex bus, which reduces the development cost, and further the production cost, of the electrical device 10. Then, in the simplex bus connection mode, since another remaining port of the two ports to be used in the duplex bus connection mode is used for feeding back output signals to be checked, the reliability of the electrical device can be increased without increasing the terminal numbers. Especially, in the case where the electrical device 10 is mounted in a single package, a cheap package having the few number of pins can be used.

By the present invention, it is not necessary to develop individually the electrical device 10 for each of the simplex bus and the duplex bus since the same electrical device 10 can correspond to the both the simplex bus and the duplex bus, which reduces the development cost, and further the production cost, of the electrical device 10. Then, in the simplex bus connection mode, since another remaining port of the two ports to be used in the duplex bus connection mode is used for feeding back output signals to be checked, the reliability of the electrical device can be increased without increasing the terminal numbers. Especially, in case the electrical device 10 is mounted in a single package, a cheap package having a few number of pins can be used.