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Portable electronic medium

  • US 6,490,667 B1
  • Filed: 09/18/2000
  • Issued: 12/03/2002
  • Est. Priority Date: 09/18/2000
  • Status: Expired due to Fees
First Claim
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1. A certification method for checking a portable electronic medium comprising:

  • a base board on which wiring is provided;

    a first memory, installed on the base board, for storing data; and

    a control circuit including;

    a second memory for storing data; and

    a control section for controlling an operation of storing data in the first memory and an operation of reading the data from the first memory, said second memory and said control section being fabricated as a chip which is installed on the base board and connected to the base board, said second memory further storing, as first-memory-state information, a recording start address at which the first memory has started to store the data at last-time processing, a length of the data stored, and a checksum for the data defined by the recording start address and the length of the data;

    wherein said certification method includes steps at which;

    when access is made to the first memory the control section determines a recording start address at which the first memory has started to store the data at the last-time processing and a length of the data stored;

    calculates a checksum for the data defined by the recording start address and the length of the data, compares the recording start address, the length of the data and the calculated checksum with the recording start address, the length of the data and the checksum, respectively, stored in the second memory as the first-memory state information and verifies the first memory when the start addresses, lengths and checksums coincide.

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