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

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.