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apple2gs: fix $C02E vertical counter readback, corrects hang in ShowMe NDA. [R. Belmont]

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This commit is contained in:
arbee 2021-04-24 16:14:03 -04:00
parent 92213dbdab
commit e7d317c44a
1 changed files with 4 additions and 23 deletions
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27
src/mame/drivers/apple2gs.cpp
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@ -2180,31 +2180,12 @@ void apple2gs_state::do_io(int offset)
} }
} }
// apple2gs_get_vpos - return the correct vertical counter value for the current scanline, // apple2gs_get_vpos - return the correct vertical counter value for the current scanline.
// keeping borders in mind.
int apple2gs_state::get_vpos() int apple2gs_state::get_vpos()
{ {
int result, scan; // as per IIgs Tech Note #39, this is simply scanline + 250 on NTSC (262 lines),
static const u8 top_border_vert[BORDER_TOP] = // or scanline + 200 on PAL (312 lines)
{ return ((m_screen->vpos() + BORDER_TOP) % 262) + 250;
0xfa, 0xfa, 0xfa, 0xfa, 0xfb, 0xfb, 0xfb, 0xfb,
0xfc, 0xfc, 0xfc, 0xfd, 0xfd, 0xfe, 0xfe, 0xff,
};
scan = m_screen->vpos();
if (scan < BORDER_TOP)
{
result = top_border_vert[scan];
}
else
{
result = scan - BORDER_TOP + 0x100 + 1;
}
return result;
} }
void apple2gs_state::process_clock() void apple2gs_state::process_clock()