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Power down state machine for PCMCIA PC card applications

  • US 5,546,590 A
  • Filed: 09/19/1994
  • Issued: 08/13/1996
  • Est. Priority Date: 09/19/1994
  • Status: Expired due to Term
First Claim
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1. A method for removing power to certain circuitry of a peripheral device, said certain circuitry comprising a microcontroller volatile and nonvolatile memory, application logic, and a microcontroller and application logic clock, said method for removing power to certain circuitry controlled by control logic of said peripheral device, said peripheral device coupled in communication with a computer system, comprising the steps of:

  • a) notifying said peripheral device to power down;

    b) notifying said microcontroller of a pending power down event;

    c) saving information in said volatile memory to said nonvolatile memory;

    d) setting a flag in said nonvolatile memory indicating said information has been saved;

    e) transferring said microcontroller to a halt state;

    f) shutting off inputs driven by said microcontroller to circuitry including said control logic of said peripheral device other than said certain circuitry to which power is to be removed;

    g) asserting and holding a reset signal to said microcontroller and said certain circuitry to which power is to be removed;

    h) disabling inputs to said certain circuitry to which power is to be removed;

    i) disabling and removing power from said microcontroller and application logic clock;

    j) removing power from said certain circuitry excluding said microcontroller; and

    k) removing power from said microcontroller.

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