ARM DS-5 Using the Debug Hardware Configuration Utilities

Debugging with your debug hardware unit8.9 Interaction between breakpoint handling in the debug hardware and yourdebuggerThe following describe the interaction between breakpoint handling in the debug hardware andbreakpoint handling in your debugger:Break details or break capabilitiesYou can find out what hardware breakpoint resources are available by viewing thebreak details or break capabilities in your debugger.Memory mapsYour debugger enables you to define a memory map to describe the layout andtype of memory in your system. When you set a breakpoint, areas of memory thatare marked as read-only, such as Flash and ROM, automatically use hardwareinstruction breakpoints. All other types of memory use software instructionbreakpoints by default.SteppingWhen you step through code, the debugger usually sets a temporary breakpointon the destination address. If the code is in read-only memory, or if the softwarebreakpoint implementation requires hardware assistance, a hardware breakpointis used for this. If you are unable to step, you might have to free up a hardwarebreakpoint resource.Some processors, such as ARM9, provide dedicated single-step hardware. debughardware uses this hardware if it is available, but steps larger than a singleinstruction might revert back to using breakpoints, to improve efficiency.NoteFor ARM7, ARM9, ARM11 or Cortex-A8 processors, interrupts are disabledwhen single-stepping with debug hardware. For the Cortex-M3 processor,interrupts are enabled when single-stepping with debug hardware.Interrupt behavior applies only to debug hardware single-instruction stepping.Higher-level stepping depends on the strategy in your debugger, that is, whetheryou have used the place Breakpoint and run method, or the multiplesingle-instruction steps method.NoteWhen hardware single-step is used, debug hardware prevents the processor fromprocessing any pending interrupts.Resource allocationDebug hardware allocates hardware breakpoint resources as they are received,rather than allocating all the resources at the same time when the debuggingsession begins. Therefore, if you attempt to set a breakpoint when there areinsufficient resources available, debug hardware displays an error message assoon as you try to set the breakpoint, rather than waiting until debugging begins.8.9.1 See alsoConcepts• Semihosting on page 8-4• Hardware breakpoints on page 8-8• Software instruction breakpoints on page 8-9• Processor exceptions on page 8-10ARM DUI 0498F Copyright © 2010-2012 ARM. All rights reserved. 8-12ID021112Non-Confidential