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https://github.com/Rockbox/rockbox.git
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e8135fea5a
Plain import of the library parts first. Adaptions to Rockbox will follow. A *lot* of kudos go to Mihaly Horvath for creating this library from his already lightweight cSID-light, mainly for Rockbox. Besides a lot of other things, he made his algorithms integer-only and significantly improved the C64 emulation, so finally RSIDs could be played as well as PSIDs. TinySID was nice for what it is, but this is a quantum leap in SID playback quality for Rockbox. Check for example: https://hvsc.csdb.dk/MUSICIANS/P/Page_Jason/Eighth.sid https://hvsc.csdb.dk/MUSICIANS/J/Jeff/Blowing.sid Change-Id: I353e12fbfd7cd8696b834616e55743e7b844a73e
64 lines
2.3 KiB
C
64 lines
2.3 KiB
C
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//VIC-II emulation
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void cRSID_createVICchip (cRSID_C64instance* C64, cRSID_VICinstance* VIC, unsigned short baseaddress) {
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VIC->C64 = C64;
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VIC->ChipModel = 0;
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VIC->BaseAddress = baseaddress;
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VIC->BasePtrWR = &C64->IObankWR[baseaddress]; VIC->BasePtrRD = &C64->IObankRD[baseaddress];
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cRSID_initVICchip (VIC);
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}
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void cRSID_initVICchip (cRSID_VICinstance* VIC) {
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unsigned char i;
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for (i=0; i<0x3F; ++i) VIC->BasePtrWR[i] = VIC->BasePtrRD[i] = 0x00;
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VIC->RowCycleCnt=0;
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}
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static inline char cRSID_emulateVIC (cRSID_VICinstance* VIC, char cycles) {
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unsigned short RasterRow;
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enum VICregisters { CONTROL = 0x11, RASTERROWL = 0x12, INTERRUPT = 0x19, INTERRUPT_ENABLE = 0x1A };
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enum ControlBitVal { RASTERROWMSB = 0x80, DISPLAY_ENABLE = 0x10, ROWS = 0x08, YSCROLL_MASK = 0x07 };
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enum InterruptBitVal { VIC_IRQ = 0x80, RASTERROW_MATCH_IRQ = 0x01 };
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VIC->RowCycleCnt += cycles;
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if (VIC->RowCycleCnt >= VIC->RasterRowCycles) {
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VIC->RowCycleCnt -= VIC->RasterRowCycles;
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RasterRow = ( (VIC->BasePtrRD[CONTROL]&RASTERROWMSB) << 1 ) + VIC->BasePtrRD[RASTERROWL];
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++RasterRow; if (RasterRow >= VIC->RasterLines) RasterRow = 0;
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VIC->BasePtrRD[CONTROL] = ( VIC->BasePtrRD[CONTROL] & ~RASTERROWMSB ) | ((RasterRow&0x100)>>1);
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VIC->BasePtrRD[RASTERROWL] = RasterRow & 0xFF;
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if (VIC->BasePtrWR[INTERRUPT_ENABLE] & RASTERROW_MATCH_IRQ) {
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if ( RasterRow == ( (VIC->BasePtrWR[CONTROL]&RASTERROWMSB) << 1 ) + VIC->BasePtrWR[RASTERROWL] ) {
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VIC->BasePtrRD[INTERRUPT] |= VIC_IRQ | RASTERROW_MATCH_IRQ;
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}
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}
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}
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return VIC->BasePtrRD[INTERRUPT] & VIC_IRQ;
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}
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static inline void cRSID_acknowledgeVICrasterIRQ (cRSID_VICinstance* VIC) {
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enum VICregisters { INTERRUPT = 0x19 };
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enum InterruptBitVal { VIC_IRQ = 0x80, RASTERROW_MATCH_IRQ = 0x01 };
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//An 1 is to be written into the IRQ-flag (bit0) of $d019 to clear it and deassert IRQ signal
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//if (VIC->BasePtrWR[INTERRUPT] & RASTERROW_MATCH_IRQ) { //acknowledge raster-interrupt by writing to $d019 bit0?
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//But oftentimes INC/LSR/etc. RMW commands are used to acknowledge VIC IRQ, they work on real
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//CPU because it writes the unmodified original value itself to memory before writing the modified there
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VIC->BasePtrWR[INTERRUPT] &= ~RASTERROW_MATCH_IRQ; //prepare for next acknowledge-detection
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VIC->BasePtrRD[INTERRUPT] &= ~(VIC_IRQ | RASTERROW_MATCH_IRQ); //remove IRQ flag and state
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//}
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}
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