[Coco] Color Forth Help Request

[Arthur Flexser]

P.S.  A plausible guess about how you wound up executing an illegal opcode
would be that somewhere the code accidentally transfers into the middle of
an instruction instead of to the instruction's first byte.

On Fri, Feb 20, 2015 at 5:54 PM, Arthur Flexser <flexser at fiu.edu> wrote:

> The only time that I'm aware of when the 6309 in emulation mode does not
> behave exactly like a 6809 is when it encounters an illegal opcode, where
> the 6309 vectors to an error location.  (The 6809 will just skip the
> illegal opcode, usually.)  So my guess would be that that's what's
> happening somewhere in Color Forth.  The 6309 error vector, not having been
> initialized to anything in particular, looks like it winds up in a section
> of the ROM CLOAD code.
>
> If the 6309 pushes registers enroute to the error vector (I'm not sure if
> it does or not, but this would be documented), you could tell what location
> the error is coming from by pointing the error vector to a routine that
> could look at the stack contents and tell you what the PC register
> contained at the time of the error.
>
> Art
>
> On Fri, Feb 20, 2015 at 5:20 PM, Stephen Pereira <spereira1952 at comcast.net
> > wrote:
>
>> Hello again, all,
>>
>> I am happy to say that I am one of the lucky ones who was able to get one
>> of the last CoCo 3 systems from Cloud-9 - I got a fully tricked out CoCo 3
>> with a Pro-Tektor, a 6309 processor, and the Triad 512K RAM upgrade (Thanks
>> a million for a great machine, Mark!).
>>
>> I discovered a problem (for me):  My Color Forth code does not run
>> properly on this machine!  What I found is that I can LOADM”CC-FORTH” and
>> EXEC just fine.  I can issue Color Forth commands (although I have not
>> attempted every command) and things seem OK.  I can issue my added DIR or
>> BASIC commands, and those works well.  Then I try to load a file of Forth
>> screens with my LSCR command.  Upon execution of that command, the CoCo
>> goes off into never-never-land.  Usually, the machine simply goes off and
>> never returns.  It does not access the disk, it just disappears.  Sometimes
>> I get a beautiful screen of scrambled graphics, but not usually.
>>
>> I had the bright idea to try all this on my VCC emulator.  The 512k RAM
>> does not make any difference.  Color Forth runs just fine.  However, when I
>> change the CPU to be a 6309, VCC fails in exactly the same way as I
>> described above on my real system.  Actually, on VCC, when I execute the
>> LSCR command with a filename, I get a blank green screen with an S in the
>> upper left hand corner, as if the machine is trying to load a cassette
>> file.  Since I removed all the cassette file code from the Color Forth
>> source code, I am puzzled why this screen appears.
>>
>> I am puzzled by this altogether.  Why should the 6309 not work like the
>> 6809, if it is supposed to be code compatible?
>>
>> I would like to hear from anyone who may be able to assist me in figuring
>> out why my code that works fine on a CoCo with a 6809 does not work on a
>> CoCo with a 6309.  Am I doomed to purchasing a 6890 and installing that
>> instead?
>>
>> Thanks very much for listening!
>>
>> --
>> Stephen M. Pereira
>> Bedford, NH  03110
>> KB1SXE
>>
>>
>> --
>> Coco mailing list
>> Coco at maltedmedia.com
>> https://pairlist5.pair.net/mailman/listinfo/coco
>>
>
>