If you use "dir bfunc" to list all the Predefined Debug Functions in uVision v2.07, the list includes 2 undocumented functions rwatch & wwatch. Keil have now added the descriptions on the support site: UV2 DEBUGGER: USING THE RWATCH BUILT-IN FUNCTION http://www.keil.com/support/docs/1815.htm UV2 DEBUGGER: USING THE WWATCH BUILT-IN FUNCTION http://www.keil.com/support/docs/1814.htm Basically, they let a Signal Function wait until a specific address is read/written.