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
+ //}
+}
+