Watchdog timer
First Claim
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1. An apparatus for generating a controlled system reset signal comprising:
- first means for sensing an initial application of electrical power and for generating said reset signal;
second means for generating a plurality of clock pulses of a selected frequency;
third means for selectively counting said clock pulses in a selected, predetermined counting sequence; and
fourth means for sensing said predetermined counting sequence including means for setting a selected indicia in response thereto and for inhibiting generation of said reset signal in response thereto.
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Abstract
A self-checking timer usable with a host system includes a clock and a plurality of interconnected counters. During a power-up phase the timer generates a system reset signal and counts the counters in a predetermined sequence. A flip-flop is set and reset during the power-up phase and inhibits generation of the system reset signal. During a normal operating phase, the timer generates a test signal that must be responded to by the host system to continuously inhibit generation of the system reset signal.
90 Citations
7 Claims
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1. An apparatus for generating a controlled system reset signal comprising:
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first means for sensing an initial application of electrical power and for generating said reset signal; second means for generating a plurality of clock pulses of a selected frequency; third means for selectively counting said clock pulses in a selected, predetermined counting sequence; and fourth means for sensing said predetermined counting sequence including means for setting a selected indicia in response thereto and for inhibiting generation of said reset signal in response thereto. - View Dependent Claims (2)
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3. A timing apparatus for monitoring the start-up and operating functions of a host system comprising:
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first means for generating a series of test signals when power is initially supplied to said timing apparatus and for determining if said timing apparatus is functioning properly; second means for removing a host system reset signal to allow said host system to begin operating after said first means has determined that said timing apparatus is functioning properly; third means for generating a test signal for transmission to said host system during operation of the host system and to which said host system must properly respond to continue operation of said host system; and means for generating said system reset signal to halt operation of said host system when said host system does not properly respond to said test signal generated by said third means. - View Dependent Claims (4, 5, 6, 7)
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Specification