dma.cpp

著名SFC模拟器Snes9x的源代码。

		    Work = *(base + p);
		    S9xSetPPU (Work, 0x2101 + d->BAddress);
		    p += inc;
		    CHECK_SOUND();
		    count -= 2;
		}
		if (count == 1)
		{
		    Work = *(base + p);
		    S9xSetPPU (Work, 0x2100 + d->BAddress);
		    p += inc;
		}
	    }
	}
	else
	if (d->TransferMode == 3)
	{
	    do
	    {
		Work = *(base + p);
		S9xSetPPU (Work, 0x2100 + d->BAddress);
		p += inc;
		if (count <= 1)
		    break;

		Work = *(base + p);
		S9xSetPPU (Work, 0x2100 + d->BAddress);
		p += inc;
		if (count <= 2)
		    break;

		Work = *(base + p);
		S9xSetPPU (Work, 0x2101 + d->BAddress);
		p += inc;
		if (count <= 3)
		    break;

		Work = *(base + p);
		S9xSetPPU (Work, 0x2101 + d->BAddress);
		p += inc;
		CHECK_SOUND();
		count -= 4;
	    } while (count > 0);
	}
	else
	if (d->TransferMode == 4)
	{
	    do
	    {
		Work = *(base + p);
		S9xSetPPU (Work, 0x2100 + d->BAddress);
		p += inc;
		if (count <= 1)
		    break;

		Work = *(base + p);
		S9xSetPPU (Work, 0x2101 + d->BAddress);
		p += inc;
		if (count <= 2)
		    break;

		Work = *(base + p);
		S9xSetPPU (Work, 0x2102 + d->BAddress);
		p += inc;
		if (count <= 3)
		    break;

		Work = *(base + p);
		S9xSetPPU (Work, 0x2103 + d->BAddress);
		p += inc;
		CHECK_SOUND();
		count -= 4;
	    } while (count > 0);
	}
	else
	{
#ifdef DEBUGGER
//	    if (Settings.TraceDMA)
	    {
		sprintf (String, "Unknown DMA transfer mode: %d on channel %d\n",
			 d->TransferMode, Channel);
		S9xMessage (S9X_TRACE, S9X_DMA_TRACE, String);
	    }
#endif
	}
    }
    else
    {
	do
	{
	    switch (d->TransferMode)
	    {
	    case 0:
	    case 2:
#ifndef VAR_CYCLES
		CPU.Cycles += 1;
#endif
		Work = S9xGetPPU (0x2100 + d->BAddress);
		S9xSetByte (Work, (d->ABank << 16) + d->AAddress);
		d->AAddress += inc;
		--count;
		break;

	    case 1:
	    case 5:
#ifndef VAR_CYCLES
		CPU.Cycles += 3;
#endif
		Work = S9xGetPPU (0x2100 + d->BAddress);
		S9xSetByte (Work, (d->ABank << 16) + d->AAddress);
		d->AAddress += inc;
		if (!--count)
		    break;

		Work = S9xGetPPU (0x2101 + d->BAddress);
		S9xSetByte (Work, (d->ABank << 16) + d->AAddress);
		d->AAddress += inc;
		count--;
		break;
		
	    case 3:
#ifndef VAR_CYCLES
		CPU.Cycles += 6;
#endif
		Work = S9xGetPPU (0x2100 + d->BAddress);
		S9xSetByte (Work, (d->ABank << 16) + d->AAddress);
		d->AAddress += inc;
		if (!--count)
		    break;
		    
		Work = S9xGetPPU (0x2100 + d->BAddress);
		S9xSetByte (Work, (d->ABank << 16) + d->AAddress);
		d->AAddress += inc;
		if (!--count)
		    break;
		    
		Work = S9xGetPPU (0x2101 + d->BAddress);
		S9xSetByte (Work, (d->ABank << 16) + d->AAddress);
		d->AAddress += inc;
		if (!--count)
		    break;
		    
		Work = S9xGetPPU (0x2101 + d->BAddress);
		S9xSetByte (Work, (d->ABank << 16) + d->AAddress);
		d->AAddress += inc;
		count--;
		break;

	    case 4:
#ifndef VAR_CYCLES
		CPU.Cycles += 6;
#endif
		Work = S9xGetPPU (0x2100 + d->BAddress);
		S9xSetByte (Work, (d->ABank << 16) + d->AAddress);
		d->AAddress += inc;
		if (!--count)
		    break;
		    
		Work = S9xGetPPU (0x2101 + d->BAddress);
		S9xSetByte (Work, (d->ABank << 16) + d->AAddress);
		d->AAddress += inc;
		if (!--count)
		    break;

		Work = S9xGetPPU (0x2102 + d->BAddress);
		S9xSetByte (Work, (d->ABank << 16) + d->AAddress);
		d->AAddress += inc;
		if (!--count)
		    break;
		    
		Work = S9xGetPPU (0x2103 + d->BAddress);
		S9xSetByte (Work, (d->ABank << 16) + d->AAddress);
		d->AAddress += inc;
		count--;
		break;

	    default:
#ifdef DEBUGGER
		if (1) //Settings.TraceDMA)
		{
		    sprintf (String, "Unknown DMA transfer mode: %d on channel %d\n",
			     d->TransferMode, Channel);
		    S9xMessage (S9X_TRACE, S9X_DMA_TRACE, String);
		}
#endif
		count = 0;
		break;
	    }
	    CHECK_SOUND();
	} while (count);
    }
    
#ifdef SPC700_C
    IAPU.APUExecuting = Settings.APUEnabled;
    APU_EXECUTE ();
#endif
    while (CPU.Cycles > CPU.NextEvent)
	S9xDoHBlankProcessing ();

    // Super Punch-Out requires that the A-BUS address be updated after the
    // DMA transfer.
    Memory.FillRAM[0x4302 + (Channel << 4)] = (uint8) d->AAddress;
    Memory.FillRAM[0x4303 + (Channel << 4)] = d->AAddress >> 8;

    // Secret of the Mana requires that the DMA bytes transfer count be set to
    // zero when DMA has completed.
    Memory.FillRAM [0x4305 + (Channel << 4)] = 0;
    Memory.FillRAM [0x4306 + (Channel << 4)] = 0;

    DMA[Channel].IndirectAddress = 0;
    d->TransferBytes = 0;
    
    CPU.InDMA = FALSE;
}

void S9xStartHDMA ()
{
    if (Settings.DisableHDMA)
	IPPU.HDMA = 0;
    else
	missing.hdma_this_frame = IPPU.HDMA = Memory.FillRAM [0x420c];

    IPPU.HDMAStarted = TRUE;

    for (uint8 i = 0; i < 8; i++)
    {
	if (IPPU.HDMA & (1 << i))
	{
	    DMA [i].LineCount = 0;
	    DMA [i].FirstLine = TRUE;
	    DMA [i].Address = DMA [i].AAddress;
	}
	HDMAMemPointers [i] = NULL;
    }
}

uint8 S9xDoHDMA (uint8 byte)
{
    struct SDMA *p = &DMA [0];
    
    int d = 0;

    for (uint8 mask = 1; mask; mask <<= 1, p++, d++)
    {
	if (byte & mask)
	{
	    if (!p->LineCount)
	    {
		uint8 line = S9xGetByte ((p->ABank << 16) + p->Address);
		if (line == 0x80)
		{
		    p->Repeat = TRUE;
		    p->LineCount = 128;
		}
		else
		{
		    p->Repeat = !(line & 0x80);
		    p->LineCount = line & 0x7f;
		}
		
		// Disable H-DMA'ing into V-RAM (register 2118) for Hook
		if (!p->LineCount || p->BAddress == 0x18)
		{
		    byte &= ~mask;
		    p->IndirectAddress += HDMAMemPointers [d] - HDMABasePointers [d];
		    Memory.FillRAM [0x4305 + (d << 4)] = (uint8) p->IndirectAddress;
		    Memory.FillRAM [0x4306 + (d << 4)] = p->IndirectAddress >> 8;
		    continue;
		}

		p->Address++;
		p->FirstLine = 1;
		if (p->HDMAIndirectAddressing)
		{
		    p->IndirectBank = Memory.FillRAM [0x4307 + ((p - DMA) << 4)];
		    p->IndirectAddress = S9xGetWord ((p->ABank << 16) + p->Address);
		    p->Address += 2;
		}
		else
		{
		    p->IndirectBank = p->ABank;
		    p->IndirectAddress = p->Address;
		}
		HDMABasePointers [d] = HDMAMemPointers [d] = 
				    S9xGetMemPointer ((p->IndirectBank << 16) + p->IndirectAddress);
	    }
	    if (!HDMAMemPointers [d])
	    {
		if (!(HDMABasePointers [d] = HDMAMemPointers [d] = 
			S9xGetMemPointer ((p->IndirectBank << 16) + p->IndirectAddress)))
		{
		    byte &= ~mask;
		    continue;
		}
		// Uncommenting the following line breaks Punchout - it starts
		// H-DMA during the frame.
		//p->FirstLine = TRUE;
	    }
	    if (p->Repeat && !p->FirstLine)
	    {
		p->LineCount--;
		continue;
	    }
// HERE
//if (p->BAddress >= 0x40 && p->BAddress <= 0x43)
//printf ("Spooling data!!!\n");
#ifdef DEBUGGER
	    if (Settings.TraceHDMA && p->FirstLine)
	    {
		sprintf (String, "H-DMA[%d] (%d) 0x%02X%04X->0x21%02X %s, Count: %3d, Rep: %s, V-LINE: %3ld %02X%04X",
			 p-DMA, p->TransferMode, p->IndirectBank,
			 p->IndirectAddress,
			 p->BAddress,
			 p->HDMAIndirectAddressing ? "ind" : "abs",
			 p->LineCount,
			 p->Repeat ? "yes" : "no ", CPU.V_Counter,
			 p->ABank, p->Address);
		S9xMessage (S9X_TRACE, S9X_HDMA_TRACE, String);
	    }
#endif
	    switch (p->TransferMode)
	    {
	    case 0:
#ifndef VAR_CYCLES
		CPU.Cycles += 1;
#else
		CPU.Cycles += 8;
#endif
		S9xSetPPU (*HDMAMemPointers [d]++, 0x2100 + p->BAddress);
		break;
	    case 1:
	    case 5:
#ifndef VAR_CYCLES
		CPU.Cycles += 3;
#else
		CPU.Cycles += 16;
#endif
		S9xSetPPU (*(HDMAMemPointers [d] + 0), 0x2100 + p->BAddress);
		S9xSetPPU (*(HDMAMemPointers [d] + 1), 0x2101 + p->BAddress);
		HDMAMemPointers [d] += 2;
		break;
	    case 2:
	    case 6:
#ifndef VAR_CYCLES
		CPU.Cycles += 3;
#else
		CPU.Cycles += 16;
#endif
		S9xSetPPU (*(HDMAMemPointers [d] + 0), 0x2100 + p->BAddress);
		S9xSetPPU (*(HDMAMemPointers [d] + 1), 0x2100 + p->BAddress);
		HDMAMemPointers [d] += 2;
		break;
	    case 3:
	    case 7:
#ifndef VAR_CYCLES
		CPU.Cycles += 6;
#else
		CPU.Cycles += 32;
#endif
		S9xSetPPU (*(HDMAMemPointers [d] + 0), 0x2100 + p->BAddress);
		S9xSetPPU (*(HDMAMemPointers [d] + 1), 0x2100 + p->BAddress);
		S9xSetPPU (*(HDMAMemPointers [d] + 2), 0x2101 + p->BAddress);
		S9xSetPPU (*(HDMAMemPointers [d] + 3), 0x2101 + p->BAddress);
		HDMAMemPointers [d] += 4;
		break;
	    case 4:
#ifndef VAR_CYCLES
		CPU.Cycles += 6;
#else
		CPU.Cycles += 32;
#endif
		S9xSetPPU (*(HDMAMemPointers [d] + 0), 0x2100 + p->BAddress);
		S9xSetPPU (*(HDMAMemPointers [d] + 1), 0x2101 + p->BAddress);
		S9xSetPPU (*(HDMAMemPointers [d] + 2), 0x2102 + p->BAddress);
		S9xSetPPU (*(HDMAMemPointers [d] + 3), 0x2103 + p->BAddress);
		HDMAMemPointers [d] += 4;
		break;
	    }
	    if (!p->HDMAIndirectAddressing)
		p->Address += HDMA_ModeByteCounts [p->TransferMode];
	    p->FirstLine = FALSE;
	    p->LineCount--;
	}
    }
    return (byte);
}

void S9xResetDMA ()
{
    int d;
    for (d = 0; d < 8; d++)
    {
	DMA [d].TransferDirection = FALSE;
	DMA [d].HDMAIndirectAddressing = FALSE;
	DMA [d].AAddressFixed = TRUE;
	DMA [d].AAddressDecrement = FALSE;
	DMA [d].TransferMode = 0xff;
	DMA [d].ABank = 0xff;
	DMA [d].AAddress = 0xffff;
	DMA [d].Address = 0xffff;
	DMA [d].BAddress = 0xff;
	DMA [d].TransferBytes = 0xffff;
    }
    for (int c = 0x4300; c < 0x4380; c += 0x10)
    {
	for (d = c; d < c + 12; d++)
	    Memory.FillRAM [d] = 0xff;

	Memory.FillRAM [c + 0xf] = 0xff;
    }
}