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:
Nov. 09, 2010
Filed:
Jun. 20, 2002
David C. Johnson, Roseville, MN (US);
Peter B. Criswell, Bethel, MN (US);
David C. Johnson, Roseville, MN (US);
Peter B. Criswell, Bethel, MN (US);
Unisys Corporation, BlueBell, PA (US);
Abstract
A system and method for modifying the hardware instruction set of an instruction processor is disclosed. The invention utilizes one or more bits of an instruction opcode and one or more programmable bits stored within the instruction processor to generate a branch address. The branch address is then used to address a storage device such as a microcode RAM to retrieve one or more microcode instructions that control execution of the instruction opcode. Address generation is controlled by selecting a previously unused instruction opcode, then modifying the programmable bits as necessary to generate a desired branch address. By loading modified microcode instructions at the branch address, instruction execution can be modified without changing the hardware design.