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| Semiconductor device |
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| Semiconductor memory device having redundant circuit |
| Accordingly, a first object of this invention is to provide a semiconductor memory device capable ... |
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| Redundant address decoder |
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| Automatic transition charge pump for nonvolatile memories |
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| High speed static BiCMOS memory with dual read ports |
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| Flexible redundancy architecture and fuse download scheme |
| What is claimed is: 1. In an integrated circuit comprising a plurality of circuit elements, some of ... |
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| Flexibilitiy for column redundancy in a divided array architecture |
| The present invention relates to an apparatus and method for implementing flexible redundancy ... |
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| Row redundancy block architecture |
| It is therefore an object of the present invention to provide a redundancy block architecture which ... |
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Fault tolerant system employing majority voting
| Details |
Inventors: Kanekawa, Nobuyasu; Ihara, Hirokazu; Kato, Hatsuhiko;
Assignee: Hitachi, Ltd. (Tokyo, JP)
Primary Examiner: Smith; Jerry
Assistant Examiner: Cass; Russell E.
Attorney, Agent or Firm: Antonelli, Terry & Stout
Input signals supplied to a plurality redundant subsystems are input to an output selecting circuit after an output of a subsystem is changed from an output signal of a subsystem having a most reliable output signal to another output signal of another subsystem having a lower reliable output signal in turn using self-diagnoses and cross-diagnoses in each subsystem according to an algorithm as follows: if any subsystem has Syndrome 1 then select the subsystem(s) which has Syndrome 1, else if any subsystem has Syndrome 2 then select the subsystem(s) which has Syndrome 2; else if any subsystem has Syndrome L-1 then select the subsystem(s) which has Syndrome L-1; else output fail safe signal. The output selecting circuit outputs a selected signal by a method of majority voting based on the output signals from the subsystems. |
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DETAILED DESCRIPTION An object of the present invention is to provide a fault tolerant system which is able to select and output a normal signal whenever there is at least one normal subsystem.
Definition of Terms The definitions of terms for use in this specification will be indicated below: Reliability of Output Signal (Reliability of Output): Probability at which an output signal is correct.
It is expressed as a function of a syndrome observed within a system.
Cross-diagnostic Result: Result of a diagnosis made among a plurality of redundant subsystems.
It is determined by a self-diagnostic result and inter-subsystem data comparison result, i.
e.
the agreement/disagreement of the output data.
A cross-diagnostic result expresses the normality/abnormality of each subsystem which is an object to-be-diagnosed.
The present invention consists principally in providing a means of a cross-diagnosis.
The cross-diagnosis is determined by respective subsystems.
That is, different results are sometimes produced, by different subsystems which are diagnostic subjects.
A cross-diagnostic result 4-i (i: natural numbers from 1 to N) indicates the cross-diagnostic result determined in the subsystem 1-i.
That is, i denotes the No.
of a subsystem which is a diagnostic subject.
Decided Result: It is determined, judging from the cross-diagnostic results 4-1-4-N collectively.
Which subsystem output is to be selected is determined by the decided result.
A decided result S-i indicates information on whether a subsystem 1-i is normal or abnormal, where i denotes the No.
of a subsystem which is an object to be decided.
In order to accomplish the above object, the present invention adopts means as follows: 1.
A subsystem which has been diagnosed as being normal in consequence of a self-diagnosis and the processed result of which agrees with that of another subsystem is regarded as being normal, and the output thereof is delivered as a final output.
2.
In the absence of a subsystem which satisfies the condition of step 1, a subsystem providing a processed result which agrees with that of another subsystem is regarded as being normal, and the output thereof is delivered as a final output
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Fault Detection 
