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Micro-controller with a built-in test circuit and method for testing the same

  • US 5,802,071 A
  • Filed: 11/17/1995
  • Issued: 09/01/1998
  • Est. Priority Date: 11/17/1995
  • Status: Expired due to Fees
First Claim
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1. A test method for testing a micro-controller sending test results to a test instrument comprising the steps of:

  • (a) obtaining a micro-controller which contains;

    (i) a program memory containing an application program memory and a test program memory, and a test control circuit which is separate from said program memory;

    (ii) a test-mode switching register in cooperation with a multiplexer for selecting either said application program memory or said test program memory for execution, or bypassing said program memory by selecting said test control circuit; and

    (b) using a test instrument to send an instruction so as to subject said micro-controller to a test procedure according to an internal test mode, an external test mode, or an application-program-read mode, wherein;

    (i) during said external test mode, said test control circuit is selected so that said test is conducted externally in said test instrument;

    (ii) during said internal test mode, said test program memory is selected such that said test conducted is internally within said micro-controller;

    (iii) after said external and internal tests are conducted, said application-program-read mode is selected so that said application will be executed.

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