B.7.7. System speed access

When a system speed access is performed during debug state, the value of the PC increases by five addresses. System speed instructions access the memory system, and so it is possible for aborts to take place. If an abort occurs during a system speed memory access, the processor enters Abort mode before returning to debug state.

This scenario is similar to an aborted watchpoint, but the problem is much harder to fix because the abort is not caused by an instruction in the main program, and so the link register does not point to the instruction that caused the abort. An abort handler usually looks at the link register to determine the instruction that caused the abort, and the abort address. In this case, the value of the link register is invalid, but because the debugger can determine which location was being accessed, you can write the debugger to help the abort handler fix the memory system.

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