ARM ARM966E-S Technical Reference Manual page 109

Debug Support
You can program one or both watchpoint units to halt the execution of instructions by
the core. Execution halts when the values programmed into EmbeddedICE-RT match
the values currently appearing on the address bus, data bus, and various control signals.
Note
Any bit can be masked so that its value does not affect the comparison.
Each watchpoint unit can be configured to be either a watchpoint (monitoring data
accesses) or a breakpoint (monitoring instruction fetches). Watchpoints and breakpoints
can be data-dependent.
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