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[Core/VDP] improved DMA fill timing accuracy (again)

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This commit is contained in:
ekeeke 2024-03-02 08:42:03 +01:00
parent 5af254cd23
commit 8c72ba0d45
4 changed files with 11 additions and 5 deletions
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16
core/vdp_ctrl.c
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@ -593,7 +593,7 @@ int vdp_context_load(uint8 *state)
void vdp_dma_update(unsigned int cycles)
{
unsigned int dma_cycles, dma_bytes;
int dma_cycles, dma_bytes;
/* DMA transfer rate (bytes per line)
@ -630,6 +630,12 @@ void vdp_dma_update(unsigned int cycles)
else if (rate == 204) rate = 198; /* 6 refresh slots per line in H40 mode when display is off */
}
/* Adjust DMA start cycle for DMA fill to take in account intial data port write */
else if (dmafill)
{
cycles += (2 * (MCYCLES_PER_LINE / rate));
}
/* Available DMA cycles */
if (status & 8)
{
@ -692,7 +698,7 @@ void vdp_dma_update(unsigned int cycles)
}
/* Process DMA */
if (dma_bytes)
if (dma_bytes > 0)
{
/* Update DMA length */
dma_length -= dma_bytes;
@ -2452,9 +2458,6 @@ static void vdp_68k_data_w_m5(unsigned int data)
/* Check if DMA Fill is pending */
if (dmafill)
{
/* Clear DMA Fill pending flag */
dmafill = 0;
/* DMA length */
dma_length = (reg[20] << 8) | reg[19];
@ -2466,6 +2469,9 @@ static void vdp_68k_data_w_m5(unsigned int data)
/* Trigger DMA */
vdp_dma_update(m68k.cycles);
/* Clear DMA Fill pending flag */
dmafill = 0;
}
}