Programming $66

[Dave Zug]

Hope I'm not missing the question:


If the position contains CODE it (or a byte preceeding it) may be 
referenced as a JSR or BRA or any other such branching opcode.

If the position contains data, it (again.. OR a byte preceeding it or 
many bytes preceeding it) will be referenced most commonly by LDX, 
(less commonly as LDY) or LDA or CMP or CMPA or many others including 
the BITwise compares. other techniques involve loading X, 
pushing offsets to stack, executing other code, adding stack offsets 
to X and calling subrt's that use X or other.

I followed one such trail and said "okay this is hard" and gave up 
that trail.

in short, JSR's point to code, LD* points to data. sometimes there is 
DATA in the code section as well though! I can't figger if this was 
on porpose (true hardcoding or security??? naah) or lazyness ("just 
put this code in the next available location"). depending on the 
"era" and  technique used to drop it in it could take longer to hide 
data in code.



> I am trying to get a handle on this.. could someone point me in the
> right direction? 
> If I think I've found a table in a 730 (Just so we are all talking about
> the same processor), that starts at an address of lets say 0085. What Op
> Code would I be looking for in the program to see where it access this
> data? 
> Looking back through Programming $65 it would seem to be 'CE  00 85'  (
> or in assembly LDX 0085 ). But looking at the ECMGUY'S dissasemblies it
> looked like the should be JSR's instead.... What am I missing?
> 
> 
> 
~~~
Dave Z. www.delanet.com/~tgp