Patent US4763296A successfully refreshed from Google Patents.
US4763296A
Expired / Lapsed
US
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Watchdog timer
Assignee: NXP USA Inc
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Filing: 1986-07-03
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Granted: 1988-08-09
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Expires: 2006-07-03
Abstract
Abstract A data processor (2) including a watchdog timer (8) comprising: a first memory (4) holding a primary operating routine for cyclic execution during operation of the data processor, an address bus (6) for addressing locations in said first memory means, a timer (10) for continuous operation during operation of the data processor and for effecting a system reset in response to the timer reaching a predetermined value, the primary operating routine including at at least one predetermined location an instruction to reset the timer, whereby in normal operation of the data processor the timer does not reach the predetermined value, wherein the data processor further includes a second memory (12) for holding the address of the location containing the instruction to reset the timer, and a comparator (16) coupled to the address bus and the timer for preventing the timer from being reset in response to an instruction to reset the timer unless the address on the address bus is held in the second memory.
Inventors
- 👤 Anil Gercekci
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 13:57
CPC Classifications
G; G06; G06F; G06F11/00; G06F11/07; G06F11/0703; G06F11/0751; G06F11/0754; G06F11/0757
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
181 words
A data processor including a watchdog timer comprising: first memory means holding a primary operating routine for cyclic execution during operation of the data processor, an address bus for addressing locations in said first memory means, a timer for continuous operation during operation of the data processor and for effecting a system reset in response to the timer reaching a predetermined value, the primary operating routine including at at least one predetermined location an instruction to reset the timer, whereby in normal operation of the data processor the timer does not reach the predetermined value, wherein the data processor further includes second memory means for holding the address of the location containing the instruction to reset the timer, and comparator means coupled to the address bus, the second memory means and the timer for comparing the address on the address bus to the address held in the second memory means and for preventing the timer from being reset in response to an instruction to reset the timer unless the address on the address bus is held in the second memory means.
Claim 2
Dependent Claim
181 words
A data processor including a watchdog timer comprising: first memory means holding a primary operating routine for cyclic execution during operation of the data processor, an address bus for addressing locations in said first memory means, a timer for continuous operation during operation of the data processor and for effecting a system reset in response to the timer reaching a predetermined value, the primary operating routine including at at least one predetermined location an instruction to reset the timer, whereby in normal operation of the data processor the timer does not reach the predetermined value, wherein the data processor further includes second memory means for holding the address of the location containing the instruction to reset the timer, and comparator means coupled to the address bus, the second memory means and the timer for comparing the address on the address bus to the address held in the second memory means and for preventing the timer from being reset in response to an instruction to reset the timer unless the address on the address bus is held in the second memory means.
Claim 3
Dependent Claim
37 words
A data processor according to claim 1 wherein the second memory means is a read-write memory until it holds the address of the location containing the instruction to reset the timer and thereafter is a read-only memory.
Claim 4
Dependent Claim
40 words
A data processor according to claim 2 wherein the comparator means is arranged to compare the address held in the second memory means with the address on the address bus when the data processor is in an instruction fetch cycle.
Claim 5
Dependent Claim
85 words
A data processsor according to claim 3 wherein the primary operating routine includes at respective predetermined locations a plurality of instructions to reset the timer and pointer means are provided for pointing to the address held in the second memory means which is expected to be next encountered and the comparator means is arranged to prevent the timer from being reset in response to an instruction to reset the timer unless the address on the address bus is that pointed to by the pointer means.
Claim 6
Dependent Claim
14 words
A data processor according to claim 4 wherein the data processor is a microprocessor.
Claim 7
Dependent Claim
14 words
A data processor according to claim 3 wherein the data processor is a microprocessor.
Claim 8
Dependent Claim
85 words
A data processor according to claim 2 wherein the primary operating routine includes at respective predetermined locations a plurality of instructions to reset the timer and pointer means are provided for pointing to the address held in the second memory means which is expected to be next encountered and the comparator means is arranged to prevent the timer from being reset in response to an instruction to reset the timer unless the address on the address bus is that pointed to by the pointer means.
Claim 9
Dependent Claim
14 words
A data processor according to claim 7 wherein the data processor is a microprocessor.
Claim 10
Dependent Claim
14 words
A data processor according th claim 2 wherein the data processor is a microprocessor.
Claim 11
Dependent Claim
40 words
A data processor according to claim 1 wherein the comparator means is arranged to compare the address held in the second memory means with the address on the address bus when the data processor is in an instruction fetch cycle.
Claim 12
Dependent Claim
85 words
A data processor according to claim 10 wherein the primary operating routine includes at respective predetermined locations a plurality of instructions to reset the timer and pointer means are provided for pointing to the address held in the second memory means which is expected to be next encountered and the comparator means is arranged to prevent the timer from being reset in response to an instruction to reset the timer unless the address on the address bus is that pointed to by the pointer means.
Claim 13
Dependent Claim
14 words
A data processor according to claim 11 wherein the data processor is a microprocessor.
Claim 14
Dependent Claim
14 words
A data processor according to claim 10 wherein the data processor is a microprocessor.
Claim 15
Dependent Claim
85 words
A data processor according to claim 1 wherein the primary operating routine includes at respective predetermined locations a plurality of instructions to reset the timer and pointer means are provided for pointing to the address held in the second memory means which is expected to be next encountered and the comparator means is arranged to prevent the timer from being reset in response to an instruction to reset the timer unless the address on the address bus is that pointed to by the pointer means.
Claim 16
Dependent Claim
14 words
A data processor according to claim 14 wherein the data processor is a microprocessor.
Claim 17
Dependent Claim
14 words
A data processor according to claim 1 wherein the data processor is a microprocessor.
Claim 18
Dependent Claim
14 words
A data processor according to claim 16 wherein the data processor is a microprocessor.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-08-09 | 1992-02-08 | 1992-08-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-08-09 | 1996-02-08 | 1996-08-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-08-09 | 2000-02-08 | 2000-08-09 | $7700.00 | Window Closed / Lapsed |