BPLCON2 undefined behavior
I think this is now completely solved. Undefined = BPLCON2 PF1 and/or PF2 is set to undocumented value 5, 6 or 7. OCS/ECS only.
Sprites and sprite priorities work identically to documented value 4 (all sprites have priority over both playfields) even if value is 5 or larger.
Normal plane mode and EHB:
If number of planes is 5 or 6 and BPLCON2 PF2 is >= 5 and if plane 5 (counting from 1) has bit set: other planes are ignored in palette selection = COLOR16 is selected. ("SWIV" score board feature). PF1 does nothing.
Dual playfield:
Any number of planes. No 5+ requirement here.
If playfield's matching BPLCON2 PFx value is >=5 and if playfield is not transparent, it is always drawn using COLOR0. PF2PRI still work normally, only color selection becomes strange. (Used in Running man / Scoopex intro's logo). If both PF1 and PF2 is >=5: both playfields disappear, only background color (and sprites) are visible.
HAM:
HAM works normally. EDIT: Most likely because "special" plane 5 is is not used in HAM to select palette indexes.
Last edited by Toni Wilen; 23 January 2018 at 12:23.
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