The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Dec. 29, 1987
Filed:
Oct. 17, 1986
Jerry R Bauer, San Jose, CA (US);
American Microsystems, Inc., Santa Clara, CA (US);
Abstract
The addresses of firmward (ROM) being interrogated to ascertain data are continuously monitored. Selected key addresses are recognized by address detection means. Timing means is then actuated to count a preset number of address accesses, system clock cycles, or other suitable timing means. A substitute address is provided to the firmware when the timer counts down. If the incoming address is in the correct sequence then the substituted address will be the same as the incoming address and correct data will be provided by the ROM. Otherwise, incorrect data will be provided. Alternately, after countdown the incoming address can be compared with the expected incoming address. If the comparison indicates identity then the incoming address can be supplied to the firmware. Otherwise, an incorrect substitute address can be provided to the input of the firmware or incorrect substitute data can be provided on the output of the firmware. In all versions correct data will only be provided if the firmware is interrogated in the correct address sequence.