diff options
Diffstat (limited to 'lib/rbcodec/codecs/cRSID/C64/VIC.c')
-rw-r--r-- | lib/rbcodec/codecs/cRSID/C64/VIC.c | 64 |
1 files changed, 64 insertions, 0 deletions
diff --git a/lib/rbcodec/codecs/cRSID/C64/VIC.c b/lib/rbcodec/codecs/cRSID/C64/VIC.c new file mode 100644 index 0000000000..1f9f736bbe --- /dev/null +++ b/lib/rbcodec/codecs/cRSID/C64/VIC.c @@ -0,0 +1,64 @@ + +//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 + //} +} + |