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funtech/supracan.cpp: transfer upper byte for DMA fill in work RAM

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* fix rebelst hex grid display
This commit is contained in:
angelosa 2024-09-25 20:35:19 +02:00
parent ea5dfa3c30
commit 6b34b1149c
1 changed files with 4 additions and 2 deletions
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6
src/mame/funtech/supracan.cpp
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@ -1333,7 +1333,7 @@ template <unsigned ch> void supracan_state::dma_w(offs_t offset, uint16_t data,
for (int i = 0; i <= m_dma_regs.count[ch]; i++)
{
// staiwbbl wants to fill both VRAM and work RAM at startup,
// and expects to transfer word for VRAM, byte for work RAM.
// and expects to transfer full count size for VRAM, half for work RAM.
// Not providing this will cause all kinds of video and logic glitches.
// TODO: pinpoint DMA modes here (at least upper bits 14-13 should do)
if (data == 0xa800)
@ -1345,7 +1345,9 @@ template <unsigned ch> void supracan_state::dma_w(offs_t offset, uint16_t data,
}
else
{
mem.write_byte(m_dma_regs.dest[ch], mem.read_byte(m_dma_regs.source[ch]));
// rebelst expects D8-D15 to be transfered for the ROZ layer hex grids.
const u8 src_byte = m_dma_regs.dest[ch] & 1;
mem.write_byte(m_dma_regs.dest[ch], mem.read_byte(m_dma_regs.source[ch] + src_byte));
m_dma_regs.dest[ch] += dest_dec ? -1 : 1;
}
}