I'm currently trying to understand how the game Shadow Dancer works (to study the feasability of an arcade Shinobi remake).
It's the first Genesis game I look into, and I understand slowly a few things.
I have an eye on a piece of code that sends the following values to the VDP Controller :
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93309400 950096D3 977F7400 0083
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R19 = $30
R20 = $00
R21 = $00
R22 = $D3
R23 = $7F
From some document, I read :
It seems incoherent to me : with bit 23 always set to 0, it'd be impossible to access RAM. So, either bit23 is always set to 1, or the preceding address must be shifted to the left one time (that is, multiplied by 2).Registers 21, 22, 23 specify the source address on the 68000 side:
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#21: S08 S07 S06 S05 S04 S03 S02 S01 #22: S16 S15 S14 S13 S12 S11 S10 S09 #23: 0 S23 S22 S21 S20 S19 S18 S17
Here the source address would be $7FD300. So, by my assumptions, either $FFD300, or $FFA600.
After viewing the RAM, it seems that's the latter, but I'd like to have a confirmation (or a correction, in case I misunderstood or miscomputed something).
Thanks