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//VIC-II emulation
void cRSID_createVICchip (cRSID_C64instance* C64, cRSID_VICinstance* VIC, unsigned short baseaddress) {
VIC->C64 = C64;
VIC->ChipModel = 0;
VIC->BaseAddress = baseaddress;
VIC->BasePtrWR = &C64->IObankWR[baseaddress]; VIC->BasePtrRD = &C64->IObankRD[baseaddress];
cRSID_initVICchip (VIC);
}
void cRSID_initVICchip (cRSID_VICinstance* VIC) {
unsigned char i;
for (i=0; i<0x3F; ++i) VIC->BasePtrWR[i] = VIC->BasePtrRD[i] = 0x00;
VIC->RowCycleCnt=0;
}
static inline char cRSID_emulateVIC (cRSID_VICinstance* VIC, char cycles) {
unsigned short RasterRow;
enum VICregisters { CONTROL = 0x11, RASTERROWL = 0x12, INTERRUPT = 0x19, INTERRUPT_ENABLE = 0x1A };
enum ControlBitVal { RASTERROWMSB = 0x80, DISPLAY_ENABLE = 0x10, ROWS = 0x08, YSCROLL_MASK = 0x07 };
enum InterruptBitVal { VIC_IRQ = 0x80, RASTERROW_MATCH_IRQ = 0x01 };
VIC->RowCycleCnt += cycles;
if (VIC->RowCycleCnt >= VIC->RasterRowCycles) {
VIC->RowCycleCnt -= VIC->RasterRowCycles;
RasterRow = ( (VIC->BasePtrRD[CONTROL]&RASTERROWMSB) << 1 ) + VIC->BasePtrRD[RASTERROWL];
++RasterRow; if (RasterRow >= VIC->RasterLines) RasterRow = 0;
VIC->BasePtrRD[CONTROL] = ( VIC->BasePtrRD[CONTROL] & ~RASTERROWMSB ) | ((RasterRow&0x100)>>1);
VIC->BasePtrRD[RASTERROWL] = RasterRow & 0xFF;
if (VIC->BasePtrWR[INTERRUPT_ENABLE] & RASTERROW_MATCH_IRQ) {
if ( RasterRow == ( (VIC->BasePtrWR[CONTROL]&RASTERROWMSB) << 1 ) + VIC->BasePtrWR[RASTERROWL] ) {
VIC->BasePtrRD[INTERRUPT] |= VIC_IRQ | RASTERROW_MATCH_IRQ;
}
}
}
return VIC->BasePtrRD[INTERRUPT] & VIC_IRQ;
}
static inline void cRSID_acknowledgeVICrasterIRQ (cRSID_VICinstance* VIC) {
enum VICregisters { INTERRUPT = 0x19 };
enum InterruptBitVal { VIC_IRQ = 0x80, RASTERROW_MATCH_IRQ = 0x01 };
//An 1 is to be written into the IRQ-flag (bit0) of $d019 to clear it and deassert IRQ signal
//if (VIC->BasePtrWR[INTERRUPT] & RASTERROW_MATCH_IRQ) { //acknowledge raster-interrupt by writing to $d019 bit0?
//But oftentimes INC/LSR/etc. RMW commands are used to acknowledge VIC IRQ, they work on real
//CPU because it writes the unmodified original value itself to memory before writing the modified there
VIC->BasePtrWR[INTERRUPT] &= ~RASTERROW_MATCH_IRQ; //prepare for next acknowledge-detection
VIC->BasePtrRD[INTERRUPT] &= ~(VIC_IRQ | RASTERROW_MATCH_IRQ); //remove IRQ flag and state
//}
}
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