Minor changes

src/vcpu.c

@@ -0,0 +1,52 @@
+#include "vcpu.h"
+#include "mem.h"
+#include "screen.h"
+
+// Program Counter (16 bits but only 12 bits used (4096 memory addresses))
+unsigned short PC;
+
+// Index register (16 bits but only 12 bits used (4096 memory addresses))
+unsigned short I;
+
+// Stack register (16 bits)
+unsigned short S;
+
+// General purpose registers (8 bits each)
+// Note last one often used as a flag register
+unsigned char R[16];
+
+// Delay timer (8 bits)
+unsigned char DT;
+
+// Sound timer (8 bits)
+unsigned char ST;
+
+// Current VCPU state
+VCPU_State State;
+
+void VCPUInit(){
+  PC=ADDR_ROM;
+}
+
+void VCPUFetch(){
+  MemRead((char *)&(State.opcode),2,PC);
+  PC+=2;
+}
+
+void VCPUDecode(){
+  char X=(State.opcode<<4) & 0xF0;
+  char Y=(State.opcode<<8) & 0xF0;
+  char N=(State.opcode<<12) & 0xF0;
+  char NN=(State.opcode<<8) & 0xFF;
+  short NNN=(State.opcode<<4) & 0xFFF0;
+}
+
+void VCPUExecute(){
+  switch(State.opcode){
+  case 0x00E0:
+    ScreenClear();
+    break
+      ;;
+
+  }
+}