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scn2674: Fix premature address rollover with 16-bit extended addresses (nw)

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This commit is contained in:
AJR 2020-01-05 15:06:32 -05:00
parent 9f93c1d348
commit ab893535b7
1 changed files with 5 additions and 3 deletions
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8
src/devices/video/scn2674.cpp
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@ -1112,6 +1112,7 @@ TIMER_CALLBACK_MEMBER(scn2674_device::scanline_timer)
const bool mbc = (charrow == 0) && (m_buffer_mode_select == 3);
const bool blink_on = (screen().frame_number() & (m_character_blink_rate_divisor >> 1)) != 0;
const uint16_t last_address = (m_display_buffer_last_address << 10) | 0x3ff;
for (int i = 0; i < m_character_per_row; i++)
{
u8 charcode, attrcode = 0;
@ -1154,10 +1155,11 @@ TIMER_CALLBACK_MEMBER(scn2674_device::scanline_timer)
blink_on);
}
address = (address + 1) & 0xffff;
if (address > ((m_display_buffer_last_address << 10) | 0x3ff))
address = m_display_buffer_first_address;
if ((address & 0x3fff) == last_address)
address = (address & 0xc000) | m_display_buffer_first_address;
else
address = (address + 1) & 0xffff;
}
if (!m_display_enabled)