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Fix address calculation for 16bit DMA transfers on GUS

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Imported-from: https://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@4055
This commit is contained in:
Sjoerd van der Berg 2017-10-03 19:49:52 +00:00
parent c27b446d67
commit 339fb9f808
1 changed files with 10 additions and 2 deletions
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12
src/hardware/gus.cpp
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@ -742,7 +742,15 @@ static void write_gus(Bitu port,Bitu val,Bitu iolen) {
static void GUS_DMA_Callback(DmaChannel * chan,DMAEvent event) {
if (event!=DMA_UNMASKED) return;
Bitu dmaaddr = myGUS.dmaAddr << 4;
Bitu dmaaddr;
//Calculate the dma address
//DMA transfers can't cross 256k boundaries, so you should be safe to just determine the start once and go from there
//Bit 2 - 0 = if DMA channel is an 8 bit channel(0 - 3).
if (myGUS.DMAControl & 0x4)
dmaaddr = (((myGUS.dmaAddr & 0x1fff) << 1) | (myGUS.dmaAddr & 0xc000)) << 4;
else
dmaaddr = myGUS.dmaAddr << 4;
//Reading from dma?
if((myGUS.DMAControl & 0x2) == 0) {
Bitu read=chan->Read(chan->currcnt+1,&GUSRam[dmaaddr]);
//Check for 16 or 8bit channel
@ -758,8 +766,8 @@ static void GUS_DMA_Callback(DmaChannel * chan,DMAEvent event) {
for(i=dmaaddr+1;i<(dmaaddr+read);i+=2) GUSRam[i] ^= 0x80;
}
}
//Writing to dma
} else {
//Read data out of UltraSound
chan->Write(chan->currcnt+1,&GUSRam[dmaaddr]);
}
/* Raise the TC irq if needed */