EECE 259 - Lab 5 - Using The Assembler and Debug Monitor.pdf

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o Explain why your program will run when you enter ‘G’ without having to specify an address o What if you changed the value of the PC and pressed ‘G’? Try it; you cannot do any damage – press reset at any time. Debugging Programs Press the reset button key0 on the DE2. We are now going to single step our program, one instruction at a time. Single stepping is a powerful debugging tool that allows us to slow down/pause the 68000 so that we can observe the execution of each instruction – one at a time. After each instruction has executed the 68000 registers are displayed so we can see what effect that instruction has had on the 68000 and also on the outside world, (e.g. turning on an LED for example). To turn on/off single stepping mode, press the ‘S’ key. You should get confirmation that single stepping mode is [ON]. You should also see a register dump to the screen and a disassembly of the first instruction that you are about to execute, i.e. you can see what the next instruction is, i.e. MOVE.B $400000,D0 Now press the ‘G’ command to start the program Hit the space key to single step (trace) the program one instruction at a time.
Using Break Points Breakpoints are another powerful debugging technique. A breakpoint can be set at an address in memory where a chosen instruction is stored. You can then run the program at full speed, but when that instruction (the one you have set a breakpoint at) is reached, the program will stop, display the 68000 registers and enter single step mode so you can trace/single step the program from that point. Up to 8 separate breakpoints can be set at 8 different instructions (they are all cleared when you press reset or execute the breakpoint kill command) Let’s set a break point at the third instruction in our program, the JMP $00800000 instruction that makes our programs loop. To do this, enter the debugger Breakpoint SET command ‘BS’ and enter the address 0080000C. You should see the following Now run the program by pressing ‘G’. When the program reaches the JMP instruction, it will print @BREAKPOINT and stop (see below). You can now single step the program from here by hitting the space bar
Page 1 and 2: Rational: The purpose of this lab i
Page 3 and 4: Enter the ‘L’ command to load a
Page 5: Note the debugger does not know whe
Page 9 and 10: Part E - Modifying a Program Go ba

EECE 259 - Lab 5 - Using The Assembler and Debug Monitor.pdf

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