Add CPU instructions.

src/cpu.ml

@@ -53,16 +53,58 @@ let inc_pc cpu count =
 let inc_cycles cpu count =
   cpu.cycles <- cpu.cycles + count
 
+let merge_bytes low high =
+  (int_of_char high) * 256 + (int_of_char low)
+
+let split_2B x =
+  let low = x mod 256 |> char_of_int in
+  let high = x / 256 |> char_of_int in
+  (high, low)
+
 let read_2B b addr =
   let low = Bytes.get b addr in
   let high = Bytes.get b (addr + 1) in
-  (int_of_char high) * 256 + (int_of_char low)
+  merge_bytes low high
+
+let inc_BC cpu =
+  let v = merge_bytes cpu.reg.c cpu.reg.b in
+  let low, high = split_2B (v + 1) in
+  cpu.reg.c <- low;
+  cpu.reg.b <- high
 
 (** http://imrannazar.com/GameBoy-Z80-Opcode-Map *)
 let run cpu (cartridge: Cartridge.t) =
-(*  Hexa.print_slice cartridge.full_rom cpu.reg.pc (cpu.reg.pc + 7) ~width:16; *)
-  match Bytes.get cartridge.full_rom cpu.reg.pc with
-  | '\x00' -> printf "  nop\n"; inc_pc cpu 1; inc_cycles cpu 4
-  | '\xC3' -> let addr = read_2B cartridge.full_rom (cpu.reg.pc + 1) in
-              printf "  jp 0x%02x\n" addr; cpu.reg.pc <- addr; inc_cycles cpu 16
-  | _ as x -> eprintf "OpCode %02X\n" (int_of_char x); failwith "Unimplemented opcode."
+  let data = cartridge.full_rom in
+  let n = Bytes.get data (cpu.reg.pc + 1) in
+  let nn = Bytes.get data (cpu.reg.pc + 2) in
+(*  Hexa.print_slice cartridge.full_rom cpu.reg.pc (cpu.reg.pc + 7); *)
+  match Bytes.get data cpu.reg.pc with
+  | '\x00' -> printf "  NOP\n";
+              inc_pc cpu 1; inc_cycles cpu 4
+
+  | '\x03' -> printf "  INC \tBC\n";
+              inc_BC cpu;
+              inc_pc cpu 1; inc_cycles cpu 8
+
+  | '\x3E' -> printf "  LD \tA, 0x%02X\n" (int_of_char n);
+              cpu.reg.a <- n;
+              inc_pc cpu 2; inc_cycles cpu 8
+
+  | '\xAF' -> printf "  XOR \tA, A\n";
+              let int_A = int_of_char cpu.reg.a in
+              cpu.reg.a <- char_of_int @@ int_A lxor int_A;
+              inc_pc cpu 1; inc_cycles cpu 4
+
+  | '\xC3' -> let addr = read_2B data (cpu.reg.pc + 1) in
+              printf "  JP \t0x%04X\n" addr;
+              cpu.reg.pc <- addr; inc_cycles cpu 16
+
+  | '\xE0' -> printf "  LDH \t(0x%02X), A\n" (int_of_char n);
+              (* fixme *)
+              inc_pc cpu 2; inc_cycles cpu 12
+
+  | '\xF3' -> printf "  DI\n";
+              (* fixme *)
+              inc_pc cpu 1; inc_cycles cpu 4
+
+  | _ as x -> eprintf "opcode %02X\n" (int_of_char x); failwith "Unimplemented opcode."