Program counter and exception

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Maartau
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Re: Program counter and exception

Postby Maartau » Sun Dec 07, 2014 11:03 am

Thanks for the infos [smilie=greencolorz4_pdt_01.gif] .
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Don't hesitate to visit http://www.atarimania.com/ & http://www.atarilegend.com/ :D

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Steven Seagal
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Re: Program counter and exception

Postby Steven Seagal » Wed Apr 29, 2015 6:08 pm

The text has been updated again.
http://www.atari-forum.com/viewtopic.php?f=94&t=24770&p=229804#p229804

The hack that runs Aladin (Macintosh emulator) was removed, now I know that MOVE.B 0,0 crashes on a real STE.

There are several bus errors where the value of PC is important.

Code: Select all

Aladin                                       move.b (a7)+,(a1)      write
Aladin                                       clr.w (a1)             write!
Aladin                                       move.w (a2),(a1)       write
Aladin                                       move.l d3,(a1)         write
Aladin                                       move.l d0,(a2)         write


Bus error = writing on address 0.
The trouble one (in Steem SSE) was clr.w (a1).
The ST may read memory there but not write into it. So it crashes after <EA>
and PC points to next instruction.
Finally a legit fix.


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