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US4686456A
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Memory test circuit
Assignee: Toshiba Corp
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Filing: 1986-03-31
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Granted: 1987-08-11
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Expires: 2006-03-31
Abstract
Abstract A memory test circuit in which test data is simultaneously written into plural memory cells of a semiconductor memory device and then subsequently read from the plural memory cells to assure reliable operation of the memory device. A logical sum and a logical product are formed of the test data read out from the plural memory cells. The logical product and the logical sum are subjected to an exclusive-or operation, the result of which is indicative of whether or not the test data was correctly written into the memory cells.
Inventors
- 👤 Tohru Furuyama
- 👤 Takashi Ohsawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 22:36
CPC Classifications
G; G01; G01R; G01R31/00; G01R31/26; G11; G11C; G11C29/00; G11C29/04; G11C29/08; G11C29/12; G11C29/18; G11C29/30; G11C29/34; G01R31/28; G01R31/317; G01R31/3181; G11C29/26; G11C29/38
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
154 words
A memory test circuit comprising: means for simultaneously writing identical test data to several memory cells; means for simultaneously reading said test data written to said memory cells; means for obtaining a first logical product operation of said test data read from said memory cells; means for obtaining a second logical sum operation of said test data read from said memory cells; and means for inspecting whether or not said memory cells having written test data operate correctly on the basis of said first logical product operation and second logical sum operation of said test data read from said memory cells; wherein said memory test circuit further comprises means for obtaining an exclusive logical sum of said logical product and logical sum of said test data and wherein an inspection of whether or not said memory cells having written test data operate correctly is carried out on the basis of said exclusive logical sum.
Claim 2
Dependent Claim
154 words
A memory test circuit comprising: means for simultaneously writing identical test data to several memory cells; means for simultaneously reading said test data written to said memory cells; means for obtaining a first logical product operation of said test data read from said memory cells; means for obtaining a second logical sum operation of said test data read from said memory cells; and means for inspecting whether or not said memory cells having written test data operate correctly on the basis of said first logical product operation and second logical sum operation of said test data read from said memory cells; wherein said memory test circuit further comprises means for obtaining an exclusive logical sum of said logical product and logical sum of said test data and wherein an inspection of whether or not said memory cells having written test data operate correctly is carried out on the basis of said exclusive logical sum.
Claim 3
Dependent Claim
53 words
A memory test circuit according to claim 1, wherein an inspection of whether or not said memory cells written said test data operates correctly is carried out on the basis of a comparison of said test data with said logical product and logical sum of said test data read from said memory cells.
Claim 4
Dependent Claim
70 words
A memory test circuit according to claim 2, wherein said memory test circuit is further provided means for controlling which selects an output of said logical product when said test data written is "1", and an output of said logical sum when said test data written is "0", when comparing said written test data with said logical product and logical sum of said test data read from said memory cells.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-08-10 | 1991-02-09 | 1991-08-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-08-10 | 1995-02-09 | 1995-08-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-08-10 | 1999-02-09 | 1999-08-11 | $7700.00 | Window Closed / Lapsed |