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System and method for write-protecting predetermined portions of a memory array

  • US 5,394,367 A
  • Filed: 03/18/1994
  • Issued: 02/28/1995
  • Est. Priority Date: 03/18/1994
  • Status: Expired due to Fees
First Claim
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1. A method for write-protecting predetermined portions of a memory array utilizing a number of lock bits settable for controlling subsequent writes to selected ones of said predetermined portions of said memory array, said method comprising the steps of:

  • defining a first memory location for containing a known value forming a soft fuse value and a second memory location for containing said lock bits;

    reading the contents of said first memory location to determine a read-out contents thereof;

    comparing said read-out contents of said first memory location to said soft fuse value;

    allowing setting and resetting of individual ones of said lock bits if said read-out contents do not correspond to said soft fuse value; and

    allowing setting and disallowing resetting of individual ones of said lock bits if said read-out contents correspond to said soft fuse value.

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