diy_disassembler

[Wouter de Waal]

Hi Ludis & all

>simple disassembler for an 8 bit CPU is easy to write.

Yup, I used the table method for the HC11. Four tables, the base one and
3 extended ones (The third one only has 4 instructions, I dunno why they
didn't put all the extended instructions in one page. Must have been
easier to code the logic this way) 

Now, the 68000 disassembler I wrote, that was much more fun. Too many
instructions and modes for a table, so you have to look at the way
the instructions are encoded. (Quite consequently for the 68K).
I used a table of  OR and AND values to get to the instruction (MOVE,
JUMP or whatever) and then coded the stuff to extract the source,
destination, mode, whatnot. There's probably a better/easier way.

>The disassemblies on my web pages were produced with this "sed" method. 

You're a braver man than I am :-) The code that I'm looking at disassembles
nicely, the data and the code are separated. Sometimes they mix code and
data and that doesn't disassemble well. Then you need a disassembler that
follows the execution thread, and walks around data areas.

Now, what I need are the hardware specs for the 808 box. In other words,
where in memory do they map the input and output ports. Ludis, I know you
know, but I can understand that you might not want to tell us... but if you
would, please?