Data processing: structural design – modeling – simulation – and em – Simulating electronic device or electrical system – Event-driven
Reexamination Certificate
2006-05-09
2006-05-09
Rodriguez, Paul L. (Department: 2123)
Data processing: structural design, modeling, simulation, and em
Simulating electronic device or electrical system
Event-driven
C712S220000, C702S183000, C707S793000
Reexamination Certificate
active
07043416
ABSTRACT:
A system and method are presented for saving and restoring the state of a diagnostic module in a microprocessor. The diagnostic module contains a complex break state machine, capable of halting the microprocessor at specified breakpoints. These breakpoints are based on combinations of instruction locations and/or data values, along with previous machine states. A problem occurs with prior art diagnostic modules when the processor returns from an exception occurring during a fix-up cycle inserted to handle a data load miss associated with an instruction located in a branch delay slot (the location immediately following a conditional branch instruction). Under these circumstances, the exception handler restores the program counter to the location of the branch instruction, causing the branch to be re-executed. The prior art state machine erroneously updates its internal state a second time when the branch is re-executed. According to the system and method disclosed herein, at each state change the previous machine state saved. Thus, when a branch instruction is re-executed, the complex break state machine of the present invention is restored to its previous state, thereby correcting the error.
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Craig Dwin M.
Daffer McDaniel LLP
LSI Logic Corporation
Rodriguez Paul L.
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