US3983329A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fail safe logic monitor
Assignee: Bendix Corp
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Filing: 1975-03-17
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Granted: 1976-09-28
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Expires: 1995-03-17
Abstract
Abstract A fail safe logic monitor wherein a multi-bit logic word is multiplexed into a comparator and compared thereby with a multiplexed "hard wired" reference word. The comparator provides an output compatible with conventional a.c. fail safe fault logic. Features of the invention include self monitoring any single internal failure for indicating a fault while the monitor is on line and automatic test ability and compatibility with existing fault logic.
Inventors
- 👤 Michael H. Rock
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 17:14
CPC Classifications
G; G06; G06F; G06F7/00; G06F7/02; G06F7/026
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
244 words
A fail safe system for monitoring a multi-bit logic word, comprising: first multiplexing means for multiplexing the multi-bit logic word; second multiplexing means for multiplexing a multi-bit reference word; first gating means connected to the first multiplexing means for gating the output therefrom; second gating means connected to the second multiplexing means for gating the output therefrom; comparator means connected to the first and second gating means and responsive to the gated outputs therefrom for providing an alternating output when the gated outputs are in substantial agreement, and otherwise providing a constant level output; first means connected to the comparator and to the first multiplexing means and responsive to the alternating comparator output for providing an address for the first multiplexing means; second means connected to the comparator and to the second multiplexing means and responsive to the alternating comparator output for providing an address for the second multiplexing means; each of the first and second means including means connected to the comparator for dividing the frequency of the alternating output therefrom, counting means connected to the frequency dividing means and to a corresponding multiplexing means, and responsive to the divided comparator output for providing the address for said multiplexing means; and the counting means in each of the first and second means being normally synchronized, with an internal system failure rendering the counters desynchronized, whereupon the gated outputs are otherwise than in substantial agreement and the comparator means provides the constant level output.
Claim 2
Dependent Claim
244 words
A fail safe system for monitoring a multi-bit logic word, comprising: first multiplexing means for multiplexing the multi-bit logic word; second multiplexing means for multiplexing a multi-bit reference word; first gating means connected to the first multiplexing means for gating the output therefrom; second gating means connected to the second multiplexing means for gating the output therefrom; comparator means connected to the first and second gating means and responsive to the gated outputs therefrom for providing an alternating output when the gated outputs are in substantial agreement, and otherwise providing a constant level output; first means connected to the comparator and to the first multiplexing means and responsive to the alternating comparator output for providing an address for the first multiplexing means; second means connected to the comparator and to the second multiplexing means and responsive to the alternating comparator output for providing an address for the second multiplexing means; each of the first and second means including means connected to the comparator for dividing the frequency of the alternating output therefrom, counting means connected to the frequency dividing means and to a corresponding multiplexing means, and responsive to the divided comparator output for providing the address for said multiplexing means; and the counting means in each of the first and second means being normally synchronized, with an internal system failure rendering the counters desynchronized, whereupon the gated outputs are otherwise than in substantial agreement and the comparator means provides the constant level output.
Claim 3
Dependent Claim
46 words
A system as described by claim 1, wherein: the counting means is responsive to the constant level output from the comparator means to stop counting, and to thereby render the system in a latched condition which is indicative of a fault in the multi-bit logic word.
Claim 4
Dependent Claim
28 words
A system as described by claim 1, wherein each of the first and second means further includes: means for resetting the frequency dividing means and the counting means.
Claim 5
Dependent Claim
82 words
A system as described by claim 1 including means for testing the second multiplexing means, said testing means including: means for applying a test signal at a predetermined logic level to the first and second gating means; the first gating means responsive to the test signal for blocking the output from the first multiplexing means; and the second gating means including means responsive to the test signal for being set by the output of the second multiplexing means for testing said means.
Claim 6
Dependent Claim
40 words
A system as described by claim 1, wherein the frequency dividing means in each of the first and second means includes: a flip-flop connected to the comparator means; and a voltage limiting device connected intermediate the comparator and the flip-flop.
Claim 7
Dependent Claim
47 words
A system as described by claim 1, wherein each of the first and second multiplexing means includes: a first multiplexer for multiplexing a portion of the bits of the word multiplexed by the multiplexing means; and a second multiplexer for multiplexing the remaining bits of said word.
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) | 1979-09-28 | 1980-03-29 | 1980-09-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-09-28 | 1984-03-29 | 1984-09-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-09-28 | 1988-03-29 | 1988-09-28 | $7700.00 | Window Closed / Lapsed |