tksim11 front-end; it works similarly)
We also have a simulator, which lets us watch what a program is
doing better than we can on the actual processor. The simulator is
called Sim6811. As with the assembler, you first
need to have gotten access to the assembler, as described in Getting Access to CS273 Software.
Once you've done this, if you execute the command
Sim6811 program.s19
you will see a screen that represents the contents of the processor. Here's an example of what that screen might look like.
A 00 B 00 t=0
D 0000
X 0000 Y 0000 breakpoints ->
SP 0000 PC F800 lds #00ff
00 (.... ....)
0 1 2 3 4 5 6 7 8 9 a b c d e f
0000 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa ................
0010 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa ................
0020 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa ................
0030 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa ................
0040 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa ................
0050 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa ................
0060 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa ................
0070 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa ................
0080 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa ................
0090 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa ................
00a0 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa ................
00b0 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa ................
00c0 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa ................
00d0 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa ................
00e0 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa ................
00f0 aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa aa ................
The current contents of the registers are shown at the top. We've
talked about the A register and mentioned the B register; we'll get to
D, X, Y, and SP later. We've also talked about the PC. The eight dots
in parentheses are the condition codes register; when a code is set,
its dot is replaced by a letter.
To the right of the PC contents is the next instruction to be executed, translated into assembly code.
The t= line tells how much time has passed (measured in
machine cycles) since the program started executing.
The big block of aa's is some of the machine's memory.
this memory, addresses 0000 through 00ff,
turns out to be the only memory that your program can read and write.
It contains aa in every byte at the moment because that's
what's in there when the simulator starts.
Each time you press the <return> key, the simulator will execute one instruction and show you the new state.