ARM Architecture Reference Manual ARMv7-A and ARMv7-R edition

C4.1.2 Debug exception on Watchpoint debug event
Debug Exceptions
If the cause of the debug exception is a Watchpoint debug event, the processor performs the following
actions:
Sets the DBGDSCR.MOE bits either to Asynchronous Watchpoint Occurred or to Synchronous
Watchpoint Occurred.
Sets the DFSR, DFAR, and DBGWFAR as described in Effects of debug exceptions on CP15 registers
and the DBGWFAR on page C4-4.
Generates a precise Data Abort exception, see Data Abort exception on page B1-55.
For more information, see Synchronous and Asynchronous Watchpoint debug events on page C3-18.
The Data Abort handler is responsible for checking the DFSR bits to find out whether the exception entry
was caused by a debug exception. If it was, typically the handler branches to the debug monitor:
The DBGWFAR indicates the address of the instruction that caused the Watchpoint debug event. see
Watchpoint Fault Address Register (DBGWFAR) on page C10-28.
LR_abt holds the address of (instruction to restart at + 8). If the watchpoint is synchronous, the
instruction to restart at is the instruction that triggered the watchpoint.
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