-------- Original-Nachricht -------- > Von: Rhialto <email@example.com> > An: CBM Hackers <firstname.lastname@example.org> > Betreff: 6809 / 6702 puzzle > Hi all, > > in the last weeks I've been putting more SuperPET features into VICE. > I'm currently testing to see how far I get running the Waterloo software > (all available from zimmers.net). Congratulations! That's a great achievement! > land. Obviously my implementation of the 6702 dongle as a simple > register isn't good enough! That was to be expected... > Can anybody see what this code is trying to do, and where it's going > wrong? I can supply more disassembly if wanted. I don't know much about the 6809, I'm basically seeing 6809 ASM for the first time... But I'll try to make out something. * It looks like those ",S" addressing modes are stack-relative, which would allow us to identify local variables * Unfortunately on 98b8 it branches back to the beginning, so it looks like a loop * on 9895 it does a branch subroutine (BSR) to 989f, but the code (data) from 9897 to 989f is not deassembled. * If I interpret the ",S++" opcodes e.g. at 989f correctly, the pull some values from the stack, so the subroutine may not be a subroutine but a jump * S,06 seems to be a pointer somewhere into memory - according to the DONGLE traces pointing to the dongle * you could make a stack dump on every cycle, as there is so much stack-relative addressing... ... but I'm afraid it seems I can't really make any sense out of this so far :-( However - now that we know the access sequence, why not write a test program with that same sequence and run it on the real machine? You could find the correct values and from those maybe deduct some logic. AndrÃ© -- Empfehlen Sie GMX DSL Ihren Freunden und Bekannten und wir belohnen Sie mit bis zu 50,- Euro! https://freundschaftswerbung.gmx.de Message was sent through the cbm-hackers mailing listReceived on 2012-02-04 22:00:03
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