8.10.5. System‑speed access

If a system‑speed access is performed during debug state, the value of the PC is increased by three addresses. As system‑speed instructions access the memory system, it is possible for aborts to take place. If an abort occurs during a system-speed memory access, ARM7DMT enters abort mode before returning to debug state.

This is similar to an aborted watchpoint except that the problem is much harder to fix, because the abort was not caused by an instruction in the main program, and the PC does not point to the instruction which caused the abort. An abort handler usually looks at the PC to determine the instruction which caused the abort, and hence the abort address. In this case, the value of the PC is invalid, but the debugger should know what location was being accessed. Thus, the debugger can be written to help the abort handler fix the memory system.

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