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Apparatus and method for detecting failure of an external device by a microcomputer

  • US 5,243,606 A
  • Filed: 12/21/1989
  • Issued: 09/07/1993
  • Est. Priority Date: 04/28/1989
  • Status: Expired due to Term
First Claim
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1. A microcomputer for use in detecting failure in an external device, said external device supplying a state signal in response to a pulse signal, comprising:

  • means for generating a pulse signal for driving said external device;

    signal holding means for holding a value in response to said state signal supplied from said external device and indicative of the state of said external device, and updating a holding value at every supplying period wherein the value held in said signal holding means changes state in response to a forward edge of said state signal; and

    failure detecting means for detecting a failure of said external device by comparing the holding value updated by said holding means with the held value updated one period before.

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