Hi Neil! :-)

 PS>> Which CPU architecture and operating system?
 NH> The original question stated that this was to be done on the 
 NH> architecture of our choice.  Do you have any suggestions?
You're asked to implement a data address breakpoint feature and you don't
have some debugger framework code to start from?

On a Unix system, you could use ptrace (man 2 ptrace). Basically you would
use PTRACE_SINGLESTEP to step through the traced process, using
PTRACE_PEEKDATA to check whether the memory location got changed. The
traced process will probably run at a snail's pace, but that's life. ;)

Ciao
Pascal

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