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Some things about the 6502 simulator "Step and Trace" function.
When you initially enter you are in the "Change Registers" mode. At
this point you can change any and all of the 6502 registers. When
done, hit ESC and you will be in the execution mode. Now you can
change and/or display memory locations, set up a break point, execute
an instruction at a time, or run at "full" speed.
When you boot or when you hit "R" while stopped in the execution mode,
you will be in the Change Registers mode. Keys have the following
meanings:
A = Change the Accumulator
C = Change the Program Counter
ESC = Go back to the execution phase
P = Change the Program Status register
S = Change the Stack Pointer
X = Change the X register
Y = Change the Y register
When you hit any of the keys above (except ESC), you will still not be
able to change the chosen register until you hit the space bar. The
contents of the register will then become high lighted and you can
change it at will. When through with a particular register. Hit
<RETURN> and the changes will be permenant. When through, hit ESC to
exit to the execution mode where the keys have the following
meanings:
C = Toggle the display of code execution (on/off)
G = GO. i.e. start code execution.
S = Toggles SUBS (???) on and off
W = Set Stop At address.
X = Wipe out current Stop At address
M = Display current memory dump start address and eight values.
Space bar highlights the contents of the first displayed memory
location. You can change it to any legal hex value and have it
accepted by typing <RETURN>. Use the arrow keys to move across to
any of the eight where you can change it.
A second "M" highlights the start address of the display. You can
change it by typing or by using either of the two horiz arrow keys
to move it eight addresses at a time. As before, acceptance is by
<RETURN>. Note that if you type in an address, the program will
force the least significant digit to either 0 or 8.